***edit- see SAFX's post...or order the whole spring kit***
I just gave Pusangani my last spare...sorry.
Ask him for one though...he should have a spare now....
I don't know about the extreme...but you don't need one in a regular hicapa. But you do then need to make sure that you're getting a full recoil stroke with the slide. If you short stroke it and don't have the spring...you'll have loading problems.

If there's other issues with your pistol...having one in there might help...don't know.
If I find a spare I'll send you a PM.
I think we used a Bic Lighter spring in ShelledPant's Hicapa? Didn't we? Can't remember if it was from a small or large bic (think it's a small...that's the size of lighter I carry now and I think that's why). We needed to stretch it out a bit and cut it to length.
Tys