Save the broken spring, it will be valuable for finding/making a replacement.
You could make a replacement w/spring steel blank (try Brownells for asst)
You could find one that's close, grind it to final shape, TotW has many spares for flint & percussion contemporary locks. Their catalog has numerous full size photos of lock parts
Your lock may be identical to locks with other brand/trade names, often imports from Italy or Spain. Or try L&R, perhaps they have a replacement of their make.