I am thinking of either getting a pair of 7.2v nimh rc batteries for the mp2 or the standard walmart 9v li-ion (tougher to find).... which is best for the mp2 and why? Thanks!
I've used 9.6v RC NiMH batts and the 9v Li-Ion and I prefer the Li-Ion b/c of its level indicator, more polished feel, form factor, and faster charging (though the NiMH chargers may have caught up in speed, I haven't used the 9.6v RC chargers in a couple years).
The Li-Ion batts aren't terribly difficult to find - Walmart doesn't make them, they simply re-brand them, as do a slew of other companies. Try searching eBay or Froogle for keywords: DVD, lithium, battery. Should get you a whole boatload of results, both 9v and otherwise. And two specific model #s of which I'm aware: Lenmar DVD-U9 and Initial RB-270.