Two possibilities to solve your search.
1) contact Larry "Stoner" Stonestreet of Stoner's Beemer Stash, Airhead Parts and Accessories
Larry Stonestreet
39628 Avenida Miguel Oeste
Murrieta, CA 82563
CA.STONER@YAHOO.COM
951-813-1704
I emailed him to find out if he had a 049 for me and he did. You might luck out.
Also try James SherlockOR
2) get a local locksmith to manufacture a key. That's what I did. I dropped off my bags, a copy of a 046 tragkorb key that I had and pictured of the 049 key I desired. One day later, the locksmith called to say my three keys were finished. Cost me $10 per key which I though was OK given the work he put into the milling and grinding.

He used an Ilco 01122C blank and milled the new key based on the info I provided him as well as the lock. He said that having the lock was better than having the 046 key although that helped to speed the process of shaping the tooth profile. What's important with these keys is the groove sizing and positioning, not the tooth profile. All keys have the same tooth profile in this series.
I've tested the keys and they work.