Will generic friction shifters work with any arbitrary set of components? It seems like they should, but I'm wondering if not all of them provide sufficient travel. Also - are there decent ones available? All I find online is the really cheap Sunrace stuff, with no reviews.

I replaced the old original Shimano indexed shifters that were integrated with the brake levers (7 speed - the bike is an early-90s MTB), with Shimano 7-speed twist grip shifters when the original ones died, and I can't get the rear to work right, so I was thinking of throwing up my hands and replacing the rear shifter with a simple friction shifter that will let me get into all the gears without hopping.

Thanks!