I know this is too late for this season, but I've been looking at cold plate ice cream carts. You plug them in the night before, load them in the morning, sell cold stuff out of them 8-10 hours, no electricity. You can have them made to hold fridge temps. I'm trying to find one with a glass lid and small flip up side table, for self service and room for some samples. The inspector OK'd it over the phone, but I'll have to prove it works before certification. They are pricey, but minimal at-market set-up and could maybe do 2 markets on 1 charge. I'll post a pic, if I find one I like.