Stopped by CampingWorld yesterday and picked up one of these:
Nature Power Solar Battery Maintainers and Trickle Chargers - 6-watt - RDK Products 40014 - Solar Panels - Camping World
Its only 6 watts so I'm not expecting much but perhaps it will be enough to stem the tide so to speak. This morning when I plugged it in and laid it out on the dash in front of the "curtain" the chassis battery had 8 volts (12 after I started and ran the engine for a few minutes).
We'll see.