I picked up one of these:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=170186517763

Came with a USB charger cable, 2x BP-5L compatible batteries, and a desktop charger (the desktop charger has no power adapter, so it requires the power adapter that comes with the N800 or the included USB adapter to work). The Nokia E61 uses the same power plug and batteries as the N800, and everything seems to work just fine. At $14 including shipping it was a pretty good deal.