Good luck!
I just picked one up in a package deal that I parted out to fix the one my grandfather left me. Like you I was unable to find anything parts wise available. Hell you cant even buy anything like a stock unless you buy the original mahogany one and even then Ruger will tell you they don't have it.

Your gunsmith should be able to build the part you need or certainly the local machine shop can.

We have a smith here that specializes in that, but at a high price

Brad

ps Try Midwestgunworks.com