There are two hand-held styles in common use: the "squeeze and strip" kind:
and the "squeeze and yank to strip" kind:
The best of the former I've got were bought about 50 years ago, but they only go up to about AWG16. No brand name on them. I bought a new pair at Lowe's (GB, as shown) a couple of months ago to handle larger wire sizes and they absolutely sucked. Your best bet, I think, today, is to prowl around military surplus vendors and look there. I go to a large airshow in Florida every year and several tool vendors show up with them there. I bought a pair there last year for about $3 and they're pretty good.
The "squeeze and yank" kind are a little harder to use, but the Xcelite brand shown is the best I've found.