Thanks a lot for your replies!
Since, unfortunately, the situation when the distributor will replace these buttons for free in case the unit is not under the warranty is not relevant in my country (I've talked to them), basically the question boils down to where exactly I can order the replacement parts.
Despite being located in Israel, I have many friends living in the US (that fly to Israel pretty often, I'm optimistic and believe that this situation with Covid 19 will end soon), so I may order in any online store that can ship these parts to them in the US or to Israel. I just need your kind advice on actual links to online stores. I haven't found any.
I've found this site:
https://store.musicservice.pl/They seem to have the parts but It looks like the only way to purchase to Israel/US is wire transfer which is something that I find less convenient (well, I might end up buying there is I won't find any store that accepts credit card payments or maybe Paypal).
I've also contacted the sales representative of
https://instrumentalparts.com/ - they've replied with a nice and really polite reply that due to the situation with Covid there are supply chains issues and they can't sell these parts right now. I can totally understand that and hope things will be better soon.
The site
https://shop.audiotronic.fr/en/genos/567-break-button-for-genos-keyboard.html that was offered by Al Ram also states that the parts are out of stock.
So any help with the actual links that you might know would be really appreciated. I don't know also whether these parts are officially coming from Yamaha (I would prefer to buy the "original" parts) but I don't know how does the procedure work that's why I'm asking for help here. Maybe I should somehow contact Yamaha US or something, but again, I don't know how exactly I should do that, so I'm out of ideas.
As for the mitigation meanwhile:
I've mapped the "break" functionality to the pedal and it works well. Since its only a hinge in the button, I consider this as a really minor (although annoying) issue and I certainly can wait. There is no rush fixing it ASAP from my side.