Sadly , I have been in the same spot . For me , it was a simple solution . I have several inverters so I ran one with several sets of xmas tree lights to provide the light needed in the time frame needed for the plants . Have also used a few "curly" bulbs off of the inverter .
I just hook the inverter to my truck/car battery and start the vehicle every few hours to recharge .
I have a generator now , so no big deal , but still use the inverters when needed .
A decent car battery will power a few 13 watt (draw) bulbs for quite awhile , and thats all you need to keep the light cycle .