Hi @alanipamolekun
Search online for [https://www.google.com/search?client=firefox-b-d&q=Google+Pixel+6a+%28GX7AS%2C+GB62Z%2C+G1AZG%29+Power+%2B+Volume+button|Google Pixel 6a (GX7AS, GB62Z, G1AZG) Power + Volume button] to find suppliers of the ***Power and Volume button*** (''not'' the ''Power'' ＆ ''Volume Button'' ''Flex Cable)'' that suit you best. (examples only)
Here's the ifixit [guide|152514] guide that will help as you will have to disassemble most of the phone to be able to insert the button in the case