I haven't been on Planet Virtual Boy in years, but I vaguely remember someone there who used to repair them. From what I remember, the best method was to solder a new set of cables between the two boards. I've been meaning to do the fix myself, but of the four or so VB's I have, only one has gotten bad enough that it is unplayable. Check around here:
www.vr32.de. Someone may be willing to repair it for you.