The push-to-connect fittings were offered this year as one of the choices in the extended
FIRST Choice KOP through AndyMark, so keep an eye out there next year too.
We order extras from a variety of places, usually chosen based on building a bigger order. Here's a T-connector for instance:
http://www.alliedelec.com/Search/Pro...&MPN=KQ2T07-00
Other common fittings are listed at the bottom of that page too. P.S. Same as Chuck's link above.