You are screwed. The transformer you will need will cost as much as a good AC powered welder.The makers dont sell power supplys for this as you use a diesel/petrol generater to run it on DC, ,,, Thats why its called an ADD on inverter ??
The person that sold it me of flebay is no longer a seller they Banned him as was advertised with leads and paperwork BUT came with none of them Tryed several ways to contact him and its no good,,,so left on my own to sort it out???
Despite what you think about the safety of rectifying the mains directly, this forum has a policy against allowing such threads. BTW, my earlier comment was made having no idea where you were. I suspected you might be from the USA, as we stopped teaching grammar here years ago. I guess the same happened in England too.
I remain surprised why this thread remains open. Perhaps you have pull with the Gods.
John