I had the same problem. Grado will not sell single parts, but they service your headphone (complete) for just usd 30$. But only if your grado is an original one, i.e. from an official grado reseller with grado serial number and not modded to death. They asked me to reassemble my headphone before sending it to grado!
Turbulent labs is selling grado replacement drivers ( turbulent x driver) for usd 130$ a pair. These drivers are excellent, i have them, slightly less bass than sr80i (unvented), great detail and resolution in one leaque with sr 225i and also sr 325is.
If you want to build your own grado, they also offer wooden cups or have a look at the post your grado mods thread my posts starting with number 3050#.
http://www.head-fi.org/t/119314/post-your-grado-mods/3045Edited by GermanGuy - 6/21/13 at 10:53am