Portable solar generators (read fancy extra-large battery packs) are still a little spendy but getting better, and there's a good selection. LED troffers don't draw all that much power, 50-60 watts for garden variety four footers, so easily 12-14 hours runtime from a 1000 Wh pack. That, or easily power 4-6 fixtures for intermittent use. A bit of up-front expense, but it also gives you the option of using the power pack in other ways (camping, picnics, power outages, etc).
Brad