I recently spoke to a tech support guy,(Jeff Langhoff) at Schiller Grounds Care which manufactures Ryan, and other turf machine products, and was told that the different reels for older model Ren-O-Thins, are still available. They are about $400 by the time you are done. They also have a wheeled stand which will hold the one (actually up to three reels) you are not using. You have to buy it through a dealer though and you need to have the exact part number for your ren o thin available because there have been lots of different models made over the years. I think the main difference is some of them had double belts and others had singles. I would get the part number from Ryan tech support and go to your dealer with it.
I think the guy said that the older Ren O Thin and the Mataway reels were the same but the newest Ren O Thin reels were different. I was asking him if a reel with spring tines as shown with the new model Ren O Thin was available (for an older RenOThin) and was told that those were different and not interchangeable. But he said the other stuff was still available. He seemed very knowledgeable. I don't want to post his email but if anybody wants it send me a PM.