We don't include the mouse button cable harness due to the expense involved in making them. They have a lot of parts and are labor intensive. The header on the boards is about as standard as possible with .100" pin spacing. Connectors for this can be found as scrap from many different sources, such as LED and switch wiring from old computer cases, internal PC CD audio cables, etc. One enterprising individual even raided the wireless phone battery recycle bin at his local Radio Shack (with permission, of course.)
The pins are not intended to be soldered to, however, so any difficulty encountered in that process would be expected.
For those without the access to scrap parts, I've added a
complete mouse button harness to the store. It comes fully assembled and has all the wire and connectors to connect 3 mouse buttons to the TurboTwist2 , EI Trackball and Opti-Wiz interface boards.
RandyT