Things you can do with your Palm Handheld.

Kokam batteries are available on eBay. These are used in aero modelling and hence have good power.. they can be and have been tried on palm(see brighthand)

This one costs- $34.95 (for 3!!)

Capacity: 2500mah Voltage: 3.7V nominal
Continuous Discharge Rate: 3C (2.5A)
Max Discharge Rate: 17.5C (17.5A)(Burst)
Dimension: 3 1/2" x 2 1/2" x 1/8"
Weight: 50.6g (1.8oz.) (each)
Combination: 3 single cells with solder tabs.
These batteries are good for any size motor up to S-400.