The AC800 uses what is called a "cobineg" negative carrier with inserts from 35mm to 6x9. This particluar type is needed to use the built in densitometer in the AC800. As well you will need the semi sunk lens board "Setopla 2839" for a 50mm lens for 35mm negs. Each of the different sizes of negs have their own light boxes as well. You can make your own test negatives by ensuring that there is a large grey patch shot under neutral conditions. The grey patch is used to calibrate the built in densitometer.

You shouldn't have any problem finding the lens boards, negative masks or light boxes on Ebay. The Cobineg may be a little more difficult.