I have found Bella Findings to be helpful, as Jeremy listed above. They do have a website, but will also work over the phone. With precious metals pricing expensive and volatile, stock changes constantly. They've been very helpful in searching stock, sending me photos to my phone, with measurements etc., and will also take photos if you have, so they can see if they have similar.
Rio Grande Jewelry is another source, with an extensive website, and lots of details about measurements and gold weights etc. They are based in Albuquerque, New Mexico, and are also pretty helpful, willing to search, chat online or phone, and seek out further details if you need.