Try giving a call around to some of the smiths that do the big bore conversions (Harton, Bowen, Huntington, Reeder, etc...) One of them is bound to have a take out cylinder in .44 laying around that you could probably purchase. A local smith could fit it for you, if it isn't a drop in fit.
Here is one for sale for $20
http://www.gunauction.com/search/displayitem.cfm?itemnum=8163067Looks to be one of the transitional new model cylinders with the recessed case heads.