Hiya Dave,
My fiddling with Ermas centers mostly around the KGPs and the earlier cast zinc guns. I checked Bob's gun parts for you, which has Erma stuff, and they are out of the individual EP-25 firing pin springs--but they still list the spring refresh kit, which would contain one of each spring for the entire gun
http://www.gun-parts.com/erma/ . In addition, I have a raft of action and fp springs I've acquired, and if we can ascertain the length, etc., I can check to see if I have one that's correct. I have one more source I could check, as well, so you'll likely wind up with a correct one. We need to know O/A length, # of coils, O.D., and wire gauge it's made from (measure with mic or calipers).
After buying my first Ermas, I Googled all over the place for info and such about them. One forum posting discussing dis-assembly said "Watch out for flying springs!" Nonetheless, I've been on my hands and knees several times, the most notable time a firing pin spring and its guide squirted out, hit the ceiling, and ricocheted into the materials rack area. The spring was almost immediately encountered on a window sill, but the guide had to wait until I cleaned and organized my stock of sheet steel--but there it was, down by the base board, behind everything. I've developed a less risky set of moves for their take-down, but a lapse in vigilance is a gun spring's worst enemy when messing with them.
Cheers, David Parker