I have one from a Sprintscan 45 (I have the scanner too but they are big so shipping would be expensive.)
It has the 6x7 insert. The 4x5 holder is very well made.
The 6x7 insert is kinda silly. They actually use magnet strips to hold it down.
I made my own magnetic strip and it works much better than the originals.
Great scanners. I moved to an Epson 700 just recently.
Anyway, the holder and insert for $50.