Only other mounts I know of that'll work are Dinan. I don't think M3 upper mounts will fit. I know the M3 lower mounts are completely different. If you're not going going to install lowering springs, Dinan mounts aren't recommended. Search rear shock mounts in this forum; there's 1 or 2 good threads..
2007 E90 335i, TiAg, 6AT, ZPP, ZSP, ZCW, 6FL, HD
Quaife lsd, ETS fmic, GIAC s/w, Dinan intake/exhaust/oc, Koni/M3 susp, Apex Arc 8, Mich PSS