The battery for the RD-1 is apparently the same as the Fuji NP-80 and Kodak KLIC-3000 battery.
These can be found on ebay relatively cheap (about $9 ea. with shipping), but I have yet to find one that is above 1400 mAh. The one B&H sells for $29 (pricey... made by CTA and is listed under accessories when you search for the Epson RD-1 on their site... I naively bought one) is only 1300 mAh (B&H describes them as being 1350 mAh). It is compatible, and although I haven't timed it, probably doesn't last as long as the one that shipped with the camera which is rated at 1500 mAh.
As to chargers, haven't fully investigated yet, but you could search for third party chargers that charge the NP-80 or KLIC-3000 battery.