Small heater for tent

I have a 2x2x48" tent on back screen porch in mid-south east FL. Winter, it can get cold sometimes and i will bring in if really cold but I will need a little 350 to 750 watt heater soon. it must have a real thermostat to be safe, can’t seem to find one, maybe there is a different product that can be repurposed? would a seed warmer do it? It will be pretty well insulated under a blanket during dark time.