Modding 3300 + HDS-3H

I was planning on attaching a headphone jack to my 3300 headset, but then realized that I don't use the mic function that often anyway. Putting the jack on the pop-port would be much more convenient, and maybe I could attach a male USB-A plug also and make it a memory stick.
Unfortunately my HDS-3 plug does not have the USB pins and the USB plug does not have the HDS pins. Does anyone know of a cable that has _all_ the pins going into the pop-port? Also, where could I get schematics of the plug and/or phone?