How quick do you need them? I'll be upgrading my trailing arms to M ones, and you can buy my current ones (the whole trailing arm). They have recent M3 bushings with Ground Control shims.
I am in no hurry. I have M arms already.. I am looking to get New M3 bushings and a set of shims (they could be used, and maybe if I put shims I wont need bushings right away)