The Graflex back, on the other hand, will take cut film magazines, which show up on ebay all the time, usually under the name 'bag mag.' I got seven of them from a local for $140 total, and now I can load up 84 sheets of film and not have to worry about running out, especially if I got out for a weekend and bring a changing bag. A search will probably turn up even more info, but here's a primer:
Basically what you're dealing with in a bag mag is 12 thin metal plates with their edges folded over to form a flange on 3 sides that will hold a sheet of film. A picture is taken, and then a rod on the holder itself is pulled, which pulls the exposed film, in its metal sheathe (called a 'septum'), out of the solid portion of the holder and into the leather bag side, at which point you manually manipulate the septum in the bag into the back of the stack in the solid side. It all sounds quite complicated, but in practice, they are incredibly simple to use and very, very easy to repair.
Here are my buying tips: make sure it has all 12 septums. It won't work without all 12 present. Make sure the septums are flat and true, bent septums can be bent back to straight, but you don't want to get something that is excessively mangled. On the inside of the metal lid there are two flat metal springs which should both be present, missing one makes the holders prone to jamming, missing both makes them inoperable. Don't worry about the bag, these holders are easy enough to take apart, and it is very, very easy to make a new bag once you've got the old one off. If you do have to make a new bag, make it a little bigger than the original, the little bit of extra space is nice to have.
Or you could just track down a Graf-lok back and some Grafmatic holders, but they only hold 6 sheets of film and usually sell for two- or three-times the price of a 'bag mag.'