I have an Endurax backpack that I got on Amazon. It holds a 17.3" laptop with no problems. It's also airline carry-on compatible. I took it with us to Hawaii and had zero issues putting it into carry-on storage. It actually fit perfectly, a lot better than I thought it would. Mine holds a Sigma 150-600mm, Sigma 70-200mm, Sig 17-70mm, and a gripped 50D and gripped 80D. I also have two YongNuo 600EX-RT II flash, Kenko rings, and a bunch of other stuff...chargers, batteries, other accessories. I like the backpack, but with everything I have in it, plus when I add the laptop, it's heavy. Not heavy enough that I couldn't hike up and down a ton of stairs while in Hawaii, we went to see some waterfalls and there was a pretty good amount of stairs, but I was a little fatigued at the end. It didn't help that it was raining but I did ok with the weight of it.
The main reason for buying it was for travel, we were planning the trip for at least a year, and I knew I wasn't going to put my gear into cargo. Took me a while to find something that would hold the big laptop and not cost a million bucks.