I have a Yamaha RM1x where some of the buttons were quite bad. I decided to replace all of them while I had it open. A couple of the encoder and the volume cap was missing so I replaced these also.
The soft buttons were Omten D3XJ and I bought these from a vendor on eBay. These are not the original ones but they seem to work perfectly. I do not know the brand or the model for the rest of the switches unfortunately as could not be seen on the buttons. The vendor is “componentalliance” and they have various spare parts for the rm1x and they are located in the UK (I am not affiliated with them in any way)