I found these on eBay:
http://www.ebay.com/sch/i.html?_from...abric&_sacat=0
I really like the Loralie Designs cat blocks ("Cool Cats"). Very colorful, whimsical, and cheerful. Although they are printed as blocks, it's very easy to re-arrange the blocks into a panel format, and you could arrange the blocks in a different order so the two quilts would be easy to tell apart.
https://www.fabric.com/SearchResults...3-26a376046a5e also has cat panels. The "Curious Cats" are more realistic looking but still whimsical.