i've been running both my M1 and D100 from a RadioShaq 6v sled i made. total cost was about $5 w/o batteries. i just use 4 Duracell D-sizes.
if you're savvy enough electronically, you can add a voltage regulator chip to maintain a constant voltage of 5v, but IMO it's perfectly fine to run the M1/D100 on 6v.
the sled i made has been going for about 17hrs and counting. i've yet to change the batteries.
marc