Hey. Sorry. I can’t find the name of those metal “covers” specifically. They are the outside of the button. I googled online and found this
https://www.fixez.com/iphone-xs-max-button-set-gold?utm_source=google_shopping&gclid=Cj0KCQjwyLDpBRCxARIsAEENsrIUrBc9HOn3qc0HRjp4YchV0j8918VfJ_EWwWkEwfJ6q2rgSO3MG9EaAlw-EALw_wcB
it is the button set referred to as a button set. I think you have have to search for it without using the term flex cable. The metal part is still considered a button since it’s the part you press on the outside…button