[Elecraft] Looking for a good battery/charging system for K1

[John Wiener]

I'll be taking my K1 to the beach this Summer on the OR coast.   I'll  
be setting up a portable vertical.  Would appreciate advice on some  
good battery(batteries) and charging system.

Looking for light weight and capable of 2-5 W for a few hours.  I  
calculate 12V 0.4A
As far as amp-hours...not sure what value makes sense  but given that  
mostly on receive, what would be a reasonable value: 800 mAH?  more?

Any good brands?  RadioShack sufficient?  I'll be carrying the stuff  
about 3/4 mile (I'm 54  hi)

Thtanks for any advice,

John
AB8O