I used buttons for the Odin 2 Mini from SakuraRetroModding on Etsy. They fit without any modifications, except that the original buttons are glued to the membrane. Thankfully, it's easy to unglue them by cutting through the glue with nails.
Here is how the unglue process looks like. The video is for RP5, but the approach is the same for the Mini.
The new buttons are quieter, have a lower profile, and feel similar to an Xbox controller overall. I'm really happy with the mod!
I am in love with the RP5. I was considering doing this mod myself. Looks great!