I do not have a copy of that body, so I am unable to verify how good these are, but if you are simply looking for a replacement for your current button, there are these:
https://iwoodstore.com/products/cover-set-fuji-gfx100rf-gfx50-hotshoe-shutter-button-wood
https://www.etsy.com/market/shutter_button_for_fujifilm_gfx100rf
These sites have contact information pages, so the builders may be able to help you.
Can anyone recommend a shutter button to go on the GFX100RF?
I see Polar Pro makes one for the x100vi, and it looks like it would fit, but I'm not sure.
Thanks.