Want to Buy B&J and/or Korona 5x7 to 4x5 Reducing Backs

I am looking for 5x7 to 4x5 reducing backs for both of my view cameras.

I have a 1920 5x7 Korona and a Burke & James 5x7 Grover.

Is it possible to cut down the more common 8x10 to 4x5 to fit? Just a thought.

Thanks - Rob

This may not be what you want to hear, but I just made an 8x10 to 4x5 reducing back using a 12x12" piece of nice plywood and a spare Horseman standard. Used only hand tools. It fits my Studio Ansco so I can shoot Fujiroid at an Art opening. I even painted it grey like the camera. Works just fine. Grover/Watson reducing backs keep popping up on eBay.

I would not recommend cutting an 8x10 back down, it will be the same, if not more work than making one.