Since Mr RTTY has no more FIGS keycaps, I have a rather simple and cheap workaround. I used one of my old crummy keycaps, painted it with "International Green" paint from my friendly Ace Hardware, and made a label with my trusty Brother labeler. I cut it with a razor blade and attached it to the keycap. I followed up with a few coats of Clear Gloss paint to help keep it in place.  Not quite original, but "good enough for government work."