Given how new the system is you likely can get Apple to replace the key caps even for free if you have access to an Apple Store. Many authorized dealers will do it for a bench fee as they have the parts or can get them in a few days.
Sadly, I don’t know what Apple has done with the new M Series keyboards. I haven’t had the need to dig into it and the few customers I’ve had got the key cap replaced for free here in the states at an Apple Store.