you're talking about the top portion of the armrest that has the indentation, right?
if so then yes, you can ... they're on backorder though ... GM is hogging all of the available stock from the supplier to fulfill new vehicle builds and warranty repairs
they will become available eventually (hopefully soon - you're not the only one who wants to do this)
actually, they were available a few months ago but there was such a run on the stock from people wanting to do exactly what you want to do that GM ran out of extra stock and is holding tight onto the supply right now
check back with me in a few weeks ...
the part number for the ebony/black interior armrest is #22796245
the following thread has lots of people talking about this and showing off theirs after they've done it