I recently put a Gemini gold bead on my GP-100 .357, and I can tell you it’s very well made and works great for me. Their response was great - I called them on a Friday and I had it in something like 10 days. I use it with a Warren Custom “One Hole” ghost ring rear and that combination is easy to pick up. I would recommend both companies, but since you asked about Gemini, I would definitely give them a call; I think I spoke to the owner, and he was great! I will eventually put one on one of my SP-101s later.
Added: I should have stated that I got the idea for both items from someone else on this forum; I don’t recall who, but I’m thankful for everything I learn here!