Mine is missing on my 87 as well. Been planning to get a donor part and switch the "weather guard" cover over.

The last two keys (124 & 201) ran me $20 a piece, and do seem to be much better then anything cut by a local locksmith. The 87 key seems worth the money, as they really hold up. The earlier security key for the 190 (201) is not near the quality of the 87 key.

I would get that spare ASAP if I were you.