Keep in mind that you wont get a whole sheet of 4x5" film exposed, as the size of the body simply doesn't allow for it. Well, perhaps with a lot of modification to the body itself, but strictly as a
back, you wont get full frame 4x5".
That said, have a look on ebay, Polaroid 545 instant backs modified with feet for the 600SE come up now and then, and sell pretty cheaply because of the lack of instant film for that holder now. I assume you could use Fuji quickloads with them, however.
Another option would be to have
Razzledog's Razzlok back fitted with feet for your 600SE. It would be a custom job, however, and I'm not sure how expensive.