For tools and materials to make these cables from scratch, there seems to be a general consenus that Hansen Hobbies (
http://www.hansenhobbies.com/) makes the best tools and provides great materials. We have a $15 economy tool (
http://www.hansenhobbies.com/product...ools/crimp_ec/) and one of the connector kits (
http://www.hansenhobbies.com/product...rkits/ck_psck/) at $21, that we also use for FRC.
I think the alternative would be to solder two PWM wires together (sacrificing one connector) to achieve this wiring layout.