I am usually most successful by finding the fabric on the manufacturer's website, then searching by the sku listed there, along with the name of the fabric line. The search engines work equally well on all sites; it's just a matter of using the best combination of search terms.
Another thought is to try the designer. Oftentimes the designer will have a bolt or two sitting around, and I've had 2 or 3 who have been happy to sell me a yard.