Eccentric bushes are available from the dealer.
(from what I've read here, anyway).
You could try a search on "negative Camber" and "bushes" and see what it shows up?
Good luck
Morat
E30 Touring 0.35 cD - more slippery than prison soap
The M3 front eccentric bushes ajust the castor angle of the front wheels, they will only have a little effect on the camber iirc. And I don't thingk you can do anything about the reasr, it's all set up by the rear beam, there's no ajustment. They weren't really designed to be lowered beyond 20mm.
im not sure if this is right but i think you can get top mounts off a later car which help with the camber, may be a slightly cheaper option than camber adjustment parts. but im not definate.