I found this site for a replacement BMW key.

The attached links to their X150 replacement keys. Note that these are not just the cases -- this is the electronics module. They claim a locksmith can set up the key, but of course, do your homework.

At $70 per key, it's worth a look.

https://www.carandtruckremotes.com/2...-c2p17155.html

Hope it helps

 

Nice find, although since they say it works with the later year X150s, it probably doesn’t work with the early X150s (forget the exact reason, single vs dual channel, or something like that).
But still, could be great for most owners.

 

I purchased a remote from there for my XF without any problem but had to go to the dealer for programming.