There are no spring "kits" I'm aware of, just the hammer spring by itself, the only other spring you may want to replace is the firing pin return spring. Wolff makes extra power springs, you just need to determine whether you need the single or double coil, I suspect single coil, but don't know for sure, Midway, Brownells, Numrich as well as Wolff sell both, see links in the FAQs and Help sticky, you'll need the trigger work instructions from the FAQs also.
Tim