I made and soldered mine myself. This is the guide I used:
dansmc.com/cables.htmI went to a couple of hobby shops, but they didn't have the brass stock I needed, so I went to the hardware store and picked up the largest diameter solid brass bolt they had. Then, I filed down the end to fit, drilled it, used a Dremel to open up the hole on one side, and cut it to length. I discovered later that it would have been easier to put the bolt in the chuck of a drill press and turn it down with a file.
For the soldering, I used a steel food can and a MAPP gas torch. This may have been a bit dangerous, given that food cans are not designed for that temp.
That said, I think I'll order a custom cable the next time I need one ;-)