Monopod with trigger handle for height adjustment?

I have a HEAVY lens (800L, 9.9 lbs) but I often don't want to lug around a tripod. I have had more luck handholding than I thought, but still would like to explore monopods as an option. Are there any nice trigger-handle monopods up to the task of such a heavy lens? Also, is it easy to accidentally trigger the height adjustment? Probably not if my hand is on it...but figured I would ask.

The short answer is no.
As far as I know the only one of any repute was the Manfrotto. All the others are very cheap knockoffs.
I had that Manfrotto, and was enamored with the idea of the auto adjust, and yes it does come in handy.

But that one trick meant far too many compromises vs. more standard monopods.
- It does not collapse enough to be very portable,
- It is finicky,
- It didn't last very long,
- It is only available in aluminum, and it's weight to rating ratio is terrible (it's heavy and can;t hold much)

- As soon as I got a 500mm, it was of no use to me anymore.

For your 800mm, you are looking for a 4 series Gitzo/Induro/Sirui/Leo​photo etc. in carbon fiber.

Just get a good Monopod and the correct head to go with it, no trigger action, no fold out legs, and no ballhead

For a head, consider this idea;
https://photography-on-the.net …/showthread.php​?t=1429801

See if you can find a Sirui P424 - just the job for my 800 F5.6 L IS. Reasonably light, well made (all my other stuff is Gitzo) and sensibly priced.

Check out CyberDyne's suggestions on heads.

I found this, but it is not only a photographic monopod...it is also a gun rest (primarily) 33" - 65" (apparently comes in 2-section only!). So no base for QR system, but you can unscrew the standard Yoke to expose threads...the only size information is provided as an accessory for shooting that mentions 1/4" x 20 thread size.

https://www.ebay.com ….m4383.l4275.c1​0#viTabs_0

The biggest Benro mono 3 section is fast to make height adjustments. It's tall so each section is long. This means you can often get it high enough using only 1 leg lock.

I've had an "Auto" (i.e., hand-triggered) Manfrotto monopod that I really loved using while it lasted. Although I was using it primarily with 70-200 and 100-400 lenses for long shooting sessions, it broke after just a couple of years. I loved its functionality enough that I purchased another one for these lighter lenses. I baby it now, though.

When I moved up to a heavier lens for birding, I decided on a Gitzo series 4 monopod. I've been very happy with it, but I really miss the "auto" feature that's been so useful to me. For heavy lenses, I can't recommend the Manfrotto's.

SYS wrote in post #18860190
I've had an "Auto" (i.e., hand-triggered) Manfrotto monopod that I really loved using while it lasted. Although I was using it primarily with 70-200 and 100-400 lenses for long shooting sessions, it broke after just a couple of years. I loved its functionality enough that I purchased another one for these lighter lenses. I baby it now, though.

When I moved up to a heavier lens for birding, I decided on a Gitzo series 4 monopod. I've been very happy with it, but I really miss the "auto" feature that's been so useful to me. For heavy lenses, I can't recommend the Manfrotto's.

Can you provide a model number, so someone could do a web search for a used unit for themself?

Wilt wrote in post #18860219
Can you provide a model number, so someone could do a web search for a used unit for themself?

Since I'm not sure whether you're referring to the Manfrotto or the Gitzo, I'll just provide the model numbers for both:

Manfrotto 3245 (apparently no longer available)

Gitzo GM4542

Thanks, I was interested in trying to find a used Manfrotto monopod. The Manfrotto 3245 was replaced by the Manfrotto 334B, but that too is no longer available but someone has one for sale at $362 .
But it seems there is still the Manfrotto 685B Neotec Monopod, but it is a bit too pricey at $210 new or $137 used for an impetuous and not-needed purchase! The OP might be interested. From my reading it appears that the folded lengths: 29.3"685B, 26.8” 334B

https://www.adorama.co​m/bg685b.html

birder_herper wrote in post #18859763
I have a HEAVY lens (800L, 9.9 lbs) but I often don't want to lug around a tripod. I have had more luck handholding than I thought, but still would like to explore monopods as an option. Are there any nice trigger-handle monopods up to the task of such a heavy lens? Also, is it easy to accidentally trigger the height adjustment? Probably not if my hand is on it...but figured I would ask.

I understand that you are looking for something else but let me make a suggestion, based on what I do.

I use a four section, three twist lock, CF monopod with my 400/2.8, fairly heavy lens (8.5 lbs). I extend both of the bottom sections fully and use the top twist lock to adjust the monopod height as needed. For shortening the monopod I loosen it lightly so there is some friction holding the lens up. For raising the lens I loosen more so the section slides out by itself. It works well for me, making small adjustments to compensate for where I'm standing, horizontal or vertical camera use, angle that I want to shoot at, etc.

Thanks for all the suggestions, everyone! So it looks like the trigger handle monopods are out of the question. I think bpalermini has the right idea!