Try flashlightlens.com, they may have a lens the same dimensions. As for the grease, when I used to work on the v10r lights, the thick silicone grease in the plumbing section for faucet repair worked great.
I like the damping from Nyogel 767A damping grease in my V11R. I tried several other lube greases not specifically sold for damping and found them all too loose for my liking. 767A is really expensive and hard to find. I used a place called MicroTools in Calif. You can also find what's called helical grease, typically used for damping camera lens controls as I understand. I don't know how to spec what level of damping you need to look for in the grease. I took a chance on 767A. The stuff is also good on some tonearm cueing mechanisms!