[Last Calls]

Hello all.
I am rebuilding my Fathers old single shot Traditional style BP pistol. It's a generic kit build, most likely a mail order or Department store jobbie from the late sixties. It's definitely a no name brand, of little or no value beyond sentimental but I'm sure you'll understand my spending the money to get it in working order again.
My question is, could anyone point me in the direction of where I could get a new Main (or is it Hammer?) Spring? I've googled and so forth, but all my hits are for Revolver Main Springs. And I'm not handy enough to craft one. My only local option is to have my Motorcylce shop weld it, but it's white metal and I know it won't hold it's elasticity. The picture I've added highlights the contour of the spring and also where the integrated retaining pin (sheared when the spring broke) would position the spring on the hammer plate. Any help or leads as to a suitable replacement would be appreciated.