Trekkie,
Since those kits are out of production, the chances of an online store having any in stock are low. You can try www.squadron.com or www.greatmodels.com
A better source is modelers who are selling their old stock. While ebay gets both good and bad reviews, I have never had a problem (knock wood) with selling or buying there. Pick a person who has had a few feedbacks and is 100% positive.
Another source is www.starshipmodeler.com in thier trading post. Here, like other trading forums, you find a set price but no insurance like on ebay. Again, if a person is found out being a bad trader, the feedback can be dramatic.
If you are interested in resin kits, www.federationmodels.com and others usually have a pretty good stock of not only kits but upgraded parts and decals. You can find links to these places at Starship Modeler and at www.Culttvman.com (who also sells some kits himself and has a very good reputation).
I have the AMT 1701 D that I might get rid of (larger scale kit) if Polar Lights announces a 1/1000 kit of it but will probably hang on to for now.
Good luck and hope you find what you are after.