Ended going to the dealer for a factory replacement. The part number is 61128386402. Cost about $40. The other supplier I found on ebay was slow to reply to emails and slow to ship.

Got the cable, plugged it in and now I have my Grom unit up and working with 12gb of music loaded on my travel drive.

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2001 E53
Build Date 10/2000
4.4 sport package
Topaz Blue/Tan
150k on the clock and crossing my fingers
Grom USB Interface