Canon Angle Finder C vs. Off Brand?

I am interested in Canon's Angle Finder C for shooting some cool angles for a bit of album-cover art, and also for skateboarding, etc shots. All of my gear is from Canon, and I am thinking I will get Canon's angle finder as well. Am I stupid to spend $175 on a Canon product that is imitated for $50 on eBay? What do you all think of sticking with Canon products over knock-offs?

My Angle Finder B fits on my 30D. You can probably pick one of these up used for about $50.

I don't know about the imitations but my Canon C finder changes diopter value when I change the magnification. That is a major drag but I just marked setting on it so not insurmountable. Still maybe hoodman or something does not do that.

I've got a cheap one of the eBay for about $70 CAD. Works amazing with skateboarding, believe me (it's what I shoot!). Just get a cheap one from Kita on ebay, he's cool and the RAVF comes with all adapters needed for all viewfinders (although mine fits right on my 30D with no adapter).