The Ibsor shutter is very like the early Prontor Press, so much so I wonder if there aren't the same. I have one with a Rodenstock lens fitted. If you search the forum you'll find there is a guy in the states who makes occasional one off conversions to enable the cameras to be used with 5x4 double sided film holders, but I think that takes the fun away from them.

However finding 9x12 plate holders is fairly easy from Europe, and film is readily available from Ilford, EFKE, Foma etc. Try or Fomafoto in Norway - both APUG sponsors.

You can also get Rollex roll film backs, I have 2. GVB in BBelgium can supply a new glass screen - I'm going to fit his Lumigrid™ type screen as the original 9x12 screens are ver dim.