In general, catalogs are often more available than search engines, and specialty resources such as Envirotext aren't as busy as general sites such as Yahoo. Particularly for search engines, check your spelling very carefully. It's almost always out there. If you don't get any hits from your search, assume that you misspelled something or constructed the search incorrectly. The next step is to use another tool.
Practice builds precision.
If you get too many hits from your search, first see what you can learn about restricting the search, and consider using a catalog or specialized tool. Remember that the Internet has plenty of champagne and snake oil. Prepare to be disappointed by sites you were sure would be good and surprised by sites that don't appear to be much at first glance.