After much procrastination, I finally went for a claimed 1500w, modified sine wave, china inverter for £19. It should be able to give me 500w. I have had good luck over the years with the direct from china stuff. Hopefully, my luck will extend to this. Although, I have scaled back my expectations to only having a jigsaw to work. If it works with anything else, then that's a bonus. The shipping is likely 3 months, or never arrives. If they start a war over there in the mean time, then I will have neither the goods nor the refund.