Read the very first paragraph
Try Aussie imports. They drive on the same side of the road as us, and sometimes get US cars cars converted. Other than that, there's no-one I can recommend per se but there are still a few companies out there that do it. If these people can't source a vehicle, probably no-one can. They're based in my hometown, and is where my Dad got his Hummer from. They know their Yankee motahs.