ECS Tuning has the blacklines:
http://www.ecstuning.com/BMW-E82-135...ght/ES2550272/
They're a little bit pricier there, but you won't have to deal with importing them/worrying about getting scammed.
Not sure if they would be willing to put a group buy together, but they previously did something like that for OEM HIDs when I had my VW.