Go around to yard sales and see if they one. You might want to ask the seller to see if it works first, most will. I got mine at a yard sale in Frankfurt, Kentucky for $2.00 and it works great.
Select as Best AnswerUndo Best Answer
A 100 watt inverter is only around USD$20 but by the sounds of it you want more power But I can not be of much help unless you tell me something more specific.
I know of a few cheaper inverting boards but do not recommend using those unless you are comfortable with building circuit boards.
One more thing are you using a 12v battery to get to 120hz almost sine wave? Because that is what I was assuming.