I have a BMW Assist mirror that also has Homelink built in. Found it on Ebay for a reasonable price. When I got it, I discovered why - the auto dim was knackered, with a small bubble already formed, that I couldn't see in the Ebay pics. I convinced the seller to rebate me $50, and then spent $99 getting it fixed at radar-mirror.com, who I'd previously used to add Homelink to my oval mirror in the M Coupe. Voila - perfect mirror now, and Homelink to boot.
'21 M2 Competition
'08 Z4 M Coupé
'19 Golf R