I have not had any wheels straightened, but about a yesr ago I was at the local BMW car delership getting parts for my Z3 .
There was a large trailer that had wheel straightening on the side, the two people were straightening auto wheels .
I asked if they worked on motorcycle wheels, specificly older BMW wheels .
One of them said they had, the older snowflake wheels are quite soft and easily reworked as long as they were not cracked .
Might want to try contacting a local BMW car dealership and see if they this work done by a similar type business .