I searched for a bug zapper with an internal battery with a decent amount of run time to no avail. It seems there is not much of a market for off the grid situations. Finally I walked into a Harbor Freight and found an option that could work.
I found a bug zapper racket that could be modified for my purposes.
I ordered some ultraviolet LEDs to save me looking like a fool running around the cabin swatting bugs out of the air. These should draw the bugs in.
I used 4-18650 cells in a 4s configuration (16.8v), this time using some battery holders from Vruzend. These are by far safer than soldering onto 18650 cells, and they can be dismantled and the batteries re-purposed easily.
I needed to use 2 buck converters to regulate voltages for both the ultraviolet LEDs (12v), and for the zapper which originally ran on 2 D batteries in series (3v).
I build a small box with a deck on the front to catch all the dead bugs I planned on killing with this device. I also added 2 anderson powerpoles so I could charge the box. One small switch was added to the side. I glued some white paper to the inside back of the box to help reflect the ultraviolet LED out of the box.
The box seems to pull the bugs into the zapping mesh. The zapper is not as powerful as a 120 v A/C zapper but it does seem to kill anything that works itself into the mesh. This quiet feature was unintended.