seems to me that if you were going to be setting up a tent or something you would need some sort of generator. I'd check the home stores for that.
Walmart/Sams have collapsible high impact plastic tables that could be set up for work spaces since you are really looking at just table tops for making waffles.
I'd check out a wholesale club for condiment setup bins if you need things that are a bit industrial which, to me, would make sense for road side.
Most electric waffle irons are 1500-1800W, which means you would need a set of pretty beefy batteries or a generator to keep it going. Generators are very loud.
if you wanted to be as portable and unplugged as possible you could get a few cast iron or cast aluminum waffle irons (Cook's Illustrated recommended the nordicware cast aluminum one) and use a portable gas cooktop or a gas or charcoal grill(don't get it too hot(!)).