I've been surfing the web for the same, but considering the work with finding the correct items in the parts list, checking the same in the piece you are repairing and then ordering on the web, the best and simplest way is ordering kits from Martin, and if you want parts not included in the kits, Martin normaly provide these also.
Beosound 3000, BL 4000, BL 8000, BG 2404,BG 5000, BG CD50, Beocord 5000, BM 901, BM 2400, BM 4000, BV S45, BV 3702. There is nothing we cannot do, but a lot of things we don't want to do!!