Advice needed on roll film back for Thornton Pickard Reflex

I'd like to get hold of a suitable roll film back for my 1930s Thornton Pickard Junior Reflex. http://www.flickr.com/photos/mattbig...7628688197883/

At the moment I have several plate holders with the camera which take (I think) two-and-a-quarter by three-and-a-quarter plates, but I'd like to get a roll film back.

I've seen a couple of cameras up for auction with 'Patent-Rollex' film backs, but I haven't seen one of those backs available on its own.

Is there an alternative way of using roll film with this camera or a different brand of back I could use?

I managed to get a few film adapters for the plate holders but haven't had much success in cutting down film to fit them.