I had moonjump for Gex 2 once. I had found it through google and added it as a cheat in Project 64. That was years ago and it was quite annoying to make it work. I can't really help you with finding it for Gex 3 :/
I actually have really cool addresses for Gex 2: All collectibles, HP, lives, power ups and even a simple speed address! The descriptions may be at bit confusing, but you should get used to it quickly. Basically, all the remotes are stored in binary numbers, for example, if you want to get the second remote of Out of Toon, you'd poke the address from "0000 0000" to "0000 0010". For power ups and speed, those share an address per world, not level. So by that logic, the address for the firefly in Smellraiser is the same as in Frankensteinfeld.
http://tasvideos.org/userfiles/info/27662086657347398
Note that this file isn't 100% complete, it misses at least two addresses for fly power ups.
As for the savestates, I guess I can also put them into the storage of this site if I zip them. But it will take me some time to look them up and send the correct ones, I hope you can wait a bit ^^