I have a snap ring tool, AKA snap ring pliers, made by Lisle, bought at Sears. I'm sure Snap-On carries them too. It can quickly be changed from a contracting mode (makes snap rings smaller) to a an expanding mode. It's critical for axle work on older Toyota Land Cruisers, another silly hobby of mine. It has two pins on the ends of its levers for the holes on snap rings. I've also got a circlip tool that's similar, but has flats with ridges for the ends of the circlips. I'd think it would work well for opening stems up temporarily.
Morgan Fletcher
Oakland, CA