Do a thread search for PATS keys, Key programming and other variations.
There are several threads with posts by Tylus and myself.
Buy blanks on E bay.
Get three blanks.
Have them cut to match your original.
Have one programmed and program the other two yourself.
With two programmed keys you can always program additional keys.
I keep four keys at any time for my PATS protected vehicles.
If I lose one I can replace it without a dealer visit.