I recently left mine loose accidentally, and had a bit of a conniption when
it dropped and let the whole thing fall at about 65 mile-hour. You might be
pleased to know that the tyres stays in the carrier even after it has
dropped at that speed. Believe me, I am even more pleased.

Suffice to say, mine has gone too. I'm currently trying to get one through
www.germanpartshaus.com. They say that they don't have them, but that sounds
like a 'we can't be botrhered selling you something that small'. Since I'm
buying another part from them, they said they'd look for one and toss it
into the package. They ship via UPS.

It's my story of a similar problem, so I don't know if you'll have any luck.

Luke