I thought there were three elements to a crossfire key fob: Physical key, remote lock/unlock circuit board with battery, and a RFID transponder to make the SKREEM happy.

Had a fob with a broken key & worn buttons, just bought one of the $7 cases with uncut key from eBay, had the key cut to match the valet key and did a mix and match. Now have a fully operational fob with new buttons.