I kept searching and found the Freedom CPAP Battery Kit. (
https://www.cpapdirect.com/parts-and-accessories/battery-power-solutions-freedom-cpap-battery-kit )

I got an extra battery for a backup, or to run in series, and a cigarette plug adapter. With USB ports, I can charge a phone or handy-talky radio.

They also have the option of a solar charger. http://www.batterypowersolutions.net/product/sunpower-solar-panel

The two batteries will have to do for now, but the solar panel is on the list for next year's Flex Spending card, if enough's left.

Thanks, again, for the input.