If you have steady hands, and patience, it is not hard to make your own wiring harness for odd-sized setups.
4P Dupont connectors and pin connectors can be had on ebay for next to nothing. Below are the ones I used, for reference.
4P Dupont Connectors: http://www.ebay.com/itm/272235660221 (Got a bag of 100, only actually used ~10)
Female Dupont Pin Connectors: http://www.ebay.com/itm/272235659912
For reference, below are my wire lengths.
As for measurements, here are my lengths for reference. My MPCNC work area is 20″ wide, 14″ deep, and 9″ high (I plan on cutting it down to 4″ high soon), the electronics are mounted 5″ below the front left leg, under the table. The Cable Chains are 38″ Front, 30″ Left, and 36″ Top (comes out at left stepper)
My lengths (with ~12″ spare wire, for stripping/routing in the electronics boxes)
Z Stepper wire: 96″ 18AWG SS 4c
Spindle Wire bundle (rpm sensor, spindle temp sensor, servos, Z Probe, Z MAX Endstop, Z MIN Endstop, light, fan, laser guide): 104″ CAT6 SS
Right Stepper: 83″ 18AWG SS 4c
Left Stepper: 52″ 18AWG SS 4c
Rear Stepper: 84″ 18AWG SS 4c
Front Stepper: 60″ 18AWG SS 4c
X/Y MAX Endstops: 82″ 22AWG SS 4c (Rear Right Corner)
X/Y Min Endstops: 27″ 22AWG SS 4c (Front Left Corner)
The endstops are not necessary, but I am using 84oz/in steppers, capable of rapidly disassembling the machine on a crash.
The AC Line for my spindle hangs from an arm, so it does not create an EMF in the cable trays.
For a most setups, you can get away with 20AWG4cSS, or even 22AWG4cSS cable for the steppers; but an extra $10 for heavier guage wire can save you a lot of headaches in the future.
For my spindle wire bundle, I used 2 runs of STRANDED shielded CAT6 cable, similar to http://www.ebay.com/itm/301380750074 It is VERY important that you use STRANDED cable, not solid. Solid wire will break after ~10 hours of operation of the mill.
For my stepper motors, I used 18AWG 4 connector stranded shielded security system cable.