Extension cables from 100i arm to amplifier control box

I need to move the Arcmate 100i arm farther from the servo amplifier box. I'm looking for a longer cable set from base of arm to box, or a set of extensions that plug into one end or the other of existing set. I have the "2 box" style of the Rj3, where the box with servo amps is separate from the control box that the Teach Pendant plugs into. Anyone found a solution for this?