At one time Charter sold the Pathfinder Convertible with both LR and WMR cylinders. Numrich has cylinders.
http://www.e-gunparts.com/product.as...ductSKU=319870
Left as an exercise for the class is whether the LR replacement cylinder is the same as the LR cylinder used in conversions and if it is, how much fitting is required to get it to work.
My neighbor the gunsmith came into a Colt SA .22 Magnum and, wanting to shoot it cheaply without splitting cases, found that he could make adapters by cutting the heads off of fired .22 WMR cases and using them to sleeve the chambers. I don't know how well it really worked, he was not a serious pistol shooter and did not keep the gun long.
You can buy such adapters at
http://www.mcace.com/adapters.htm
but you'd have to get two sets of three at $20 each and I don't know how well they would work in a revolver instead of a rifle.