Jersey usually needs 2 layers to work well at all. It's really worth just buying interlock unless the cover pattern u plan on using requires 2 layers.
http://www.naturesfabrics.com/wool-fabrics.html
they have some nice interlock at decent prices and it u put in the code "20coop" u get 20% off.
FYI the $19 a yard interlock requires 2 layers for a cover.
If u can stand to wait the 95%merino5%lycra blend is to die for, it's wonderfully thick, stretchy and u can wash it in your machine on gentle.