Does it need to be exactly 1" thick or "about" 1" thick?
If "about" 1" thick is acceptable, I would just make my own using a sheet of 1/2" thick MDF, cutting it out into 2() 3'x5' pieces and gluing them together.
That's exactly what I did for my workbench top and it has worked out very well. HOWEVER, it does not get used as an MFT top.
Andy