I'm starting to think it would be easier to just sell it to someone in 240V land or even just cut your losses and give it to them for the cost of postage and buy a 120V version. Or use a stepup transformer, or make an adapter to get 240V from two branch circuits on opposing sides of the panel.
Adding info to old thread.
I have an 858D clone (SumSour to be exact) and I only see one very small transformer inside it. Taking a close look for the first time, I see no voltage or power spec labels anywhere on the unit! And it isn't clear to me that the little transformer is a mains unit.
The 858D transformer only powers the controls. (The heating element runs directly off AC mains.) The tiny yellow-taped transformer on the Sumsour board is part of a switching supply; the larger case-mounted transformer in other makes/versions drives a linear supply.