I don't know about Yankee Junction, but you might try Backdrop Warehouse. They seem to have a large selection of different backdrops, including clouds.
http://www.backdropwarehouse.com/TnCloudsGrp.htm
Hello,
Planning My N scale Shelf Layout and wondering if anyone Knows if The Yankee Junction Sky Backdrop is still available for Purchase?I really liked the one i used many years ago.They used to advertise in MR Magazine,Any help would be appreciated.
Thanks Hogwire