Since I found that most sear springs require very little power to do their job, an old clock spring will provide you with a lifetimes worth of raw material, same goes for a recoil spring off of an old lawnmower. If you truly need a stronger spring a tine from an old metal leaf rake works very well. My Jukar pistol has a rake tine sear spring in it, and is a living example of all the different projects I’ve attempted over the years.
I congratulate you for trying to fix something yourself instead of doing the wallet quick draw.
Hungry Horse