What about a small solar powered fence charger? I don't know if this would work, just thinking off the top of my head. I was just thinking that you could have two metal screens very close to each other in front of the light. Using the cheap silver clamp on light fixtures from walmart. mount the two screens on the end of the fixture, maybe with some of the rubber bolt on wire holders...they are insulated with rubber to keep wire from chaffing. Put the hot on one screen and the ground on the other, have the screens offset and as close together as possible. That way the possibility of the insect touching both screens will be high. The screen i am talking about is the kind like is used on the floor of chicken or rabbit coops. You can get it smaller. Like 1/4" holes. Maybe using a flouresent (sp?) light or even an led to save power. The little fence chargers can be had pretty cheaply. You are charging a very small area, so anything that would charge a 1/4 acre would probably knock the snot out of a bug. Don't know if it would work, but would be cheap and off the grid if you could do it. The fence charger would be self contained.