I got ahold of a gentleman named David Day, who built it, and was told the base was a Black and Decker Workmate with a plywood top with a 2x4 attatched to the bottom, that was then clamped in the top jaws.
I can't find the model Workmate that he used in the picture, and hope he can get back to me with whatever info is on the unit, but the WM 375 with handtruck [retail $79.95 at Aubuchon] is close, and would probably work with a little change to the shape of the top.
I still working on it.