From your avatar photo, it appears taht you've got the older style, Krauser bags.. I don't think that replacement keys are easily obtained for these. The later BMW factory bags have code and/or can be rekeyed by a locksmith. I don't think that the Krauser style bags actually had many different key configurations though..
For what its worth, I don't have keys for my old Krausers either. I DO use safety straps around them to make sure they stay closed (the design is somewhat notorious for having the lids open up at very unfortunate times)