Since these are just basic pins, (with round ends that stick slightly above the frame surface), I would make replacements from finishing nails if I were you. You can easily turn them down to the proper diameter and round off the ends with sandpaper and a hand drill if you don't have more sofisticated tools.
If you simply
must have original (or exact reproduction) pins, then check with David Chicoine
Old West Gunsmith (and author). If he doesn't have any, then they probably can't be found. I have a few, but they are happily residing in the frames of the guns they came in!
Good luck,
Chris Taylor