Is there a print or online resource for locating plants (places where they are sold)?
You can search the Andersen Horticultural Library’s Plant Information Online. But be aware that they only include a selection of nurseries (those who post their inventory online). Most local nurseries are not included, as their inventory changes too frequently. There is another website, Plant Lust, which simultaneously searches 80 different nursery catalogs (especially Oregon-based nurseries). You can also search using your favorite search engine for the name of the plant you are seeking plus the word nursery. This will not give you any clues, however, as to the reputation of the nurseries which show up in your search results. The website of Dave’s Garden does have a forum of nursery reviews (called Garden Watchdog) you can consult.