Lots of good info above. I'd start with the classifieds, as it may be the easiest. If not,, a bit of searching will turn up what you desire.
blueroan, you are correct in that you can find stuff at Brownells sometimes when others don't have it.
However,,, the OP has asked for a specific grip frame, and suggesting a change to a different one isn't offering any help. Each person has a different grip feel when they grasp a handgun. What works for you, me, or anybody else may not work for them.