There used to be a place over near Irving Place that carried that type of stuff. I remember walking by one night a few years back and being greeted by vividly colored lugged steel frames in the window. So, east side between Irving and 3rd in the mid/upper teens.
I believe the store krisdrum is referring to is on east 17th street. They opened up an annex on 15th and Irving Place also. Check out R&A Cycles web page. Look under the "sale" or "clearance" section. They used to have lots of steel Casatis there. In general, I think smaller, older shops would be your best bet.
A forum community dedicated to Road Bike owners and enthusiasts. Come join the discussion about bike parts, components, deals, performance, modifications, classifieds, troubleshooting, maintenance, and more!