You don't say wheter it's the 6.9x9 or 9x12 version. If it's the 6.5x9 don't bother with sheet film, find a 6x9 Rollex or Rada 6x9 roll film back but make sure it's the correct fit, the edges differ and there's a few versions.

9x12 cameras are easier as 9x12 is a standard continental european standard size for sheet film, you just need film adapters for the plate holders. You can also get 6x9 roll film backs for 9x12 cameras.

In practice the register difference isn't noticeable in results even at wider apertures.