Must be great timing - the molded connected-end of my cable broke yesterday, right at the power pack end. There's enough slack in the two internal wires to lay the molded stress-relief part of the cable flat against the end of the power pack. I used a sample pack of Shgru.com to make a custom rubber protector for the exposed wires & strain-relief. It is no longer the weakest part of the ensemble - that honour now goes to my left knee.
Standard safety disclaimer applies - DO NOT LISTEN TO MUSIC WHILE RIDING! You'll inevitably end up dancing on your board, misjudge the upcoming dip, and at that point the best you can hope to achieve is a left-shoulder-to-backwards-roll-popup-and-jog that lands in time with the beat.
(OMG - serious bonus points for landing the roll on the beat!!!)
TLDR: get some Shgru.com and make your own ruggidized power pack!