Cant remember what it was.... in school we made electrical testors with a clear tube and an LED light. Poured some sort of clear epoxy/resin stuff into them when done with the wiring. Slick Merc, Ive seen it out a few times
Here is a clear casting epoxy - don't know how it would be for fixing your wheel. When I searched for clear epoxy, I got lots of hits - they even sell a variety at Walmart. http://www.smooth-on.com/Castable-Epoxy-Res/c1295_1377/index.html