Widners or Western Gun Parts is likely your best bet, though I've not contacted either in some time. The Springs are indeed leaf or 'V' springs and there are two different sizes; one for the smaller gauges and another for the 12 ga. guns. Both vendors are well aware of the difs., but it never hurts to confirm that with whomever you speak to. It would make good sense to have a set of calipers and the old one on hand to be sure you are both speaking the same language, JIC you get someone not that familiar w/them as they 'look' the same & your friend is going to need the smaller ones.
In the FWIW, dept. there were also several iterations of ejectors utilized in the guns so fitted, but the hammer springs were the same throughout, excepting the size difs. already mentioned. Installing them is fair brutal, even with the proper special tool. Be prepared for a bit of frustration, before success.
