I bought the 500LE from Costco.com and was quite happy with it initially, except that I was going through tons of AAAs (a set only seemed to last a few hours, though I never did a timed test), so the rechargeable Li-ion was a must have for me to even consider keeping the unit.
So, I put in an order for two of the $20 charger/battery combos and when my order was still showing 'backordered' after two weeks, I called up Magellan directly. Took a bit of explaining to the customer rep what I was trying to do, but I basically just ordered two of the A/C chargers and two of the batteries (which you'll notice are not individually shown as backordered, only the combo is) and asked to be discounted the difference between those items and the 'special deal'. Surprisingly enough, they did it and I received my order in about a week.
Worked for me, but YMMV.