i recently bought shimano LX brakes for my trek 6500. The stock breaks it came with were shoddy pieces of junk. Anyway i noticed that the brake post ( the post that screws into the frame that the brake pivot on, not sure if thats the right name) seem to be too short for the new LX brakes they only go about 3/4 of the way through them.

My question is where can I buy new, longer, brake posts? i looked around a bit and havent found any online any ideas? the bike shops around me suck and never have anything so if anyone knows of a place online please let me know.
Thanks!