You need at least 2-4 inches larger on each dimension so I'd say you need to get a full size batting and cut it down. You can use the leftovers for pot holders and crafty projects.
http://www.stcroixquilters.com/quiltbbatting.htm
As for the backing, you may be able to get by with a single width of fabric (as long as it is AT LEAST 42" wide) by 64" long which is roughly 1 3/4 yard.