Can you clarify what you are trying to do? Are you trying to run a 240v device on 110v electricity? What type of device is it? What do you mean by "aftermarket female line cord"?
UK to US step up/down voltage converter
Does anyone know of a step up/down device into which I can connect a UK line cord (male) through to an aftermarket female line cord? Nothing I have been able to find has the requisite fittings. Am I missing something really obvious? This doesn't seem to me at all exotic.