Hi, yes you can find them at PnP's, lately there's more than there used to be. The gears can be restored if they're frozen, I've done that to several over the years, lube with something penetrating and they all have loosened up. Also you can buy the little retainers that the ball end of the plastic adjusting bolt sits in. They don't seem to seize there but they can get broken.

Cleaning,yeah, it's a good idea, the best I heard which I think is in the FAQ was to take 'em out, fill with half water, half alcohol, and a single drop of dish detergent; no more, no kidding; seriously suds up. Let it soak, then rinse.
If the lens is off, because sometimes the adhesive loosens up from weather, Do Not touch or wipe the silver reflector, the silver will come off.
Mine are pretty much like new, esp after going over the lens with Tap Plastics scratch remover. There's different grades, the fine is the best choice, the coarser ones are too much. That's probably the best thing I did to mine, it's amazing.