With most thrift stores, it's hit or miss. I know there are a few on 23rd street between 2nd & 3rd:
Goodwill --- lots of great finds in there
Salvation Army --- mostly junk
City Opera --- nice stuff, but kind of expensive
23rd St, off Lex (I think it's off Lex), there's a Housing Works thrift shop --- really great stuff and the prices are very reasonable.
There are also plenty of thrift shops all over Manhattan.... I'm sure if you Google or Bing "Thrift Shops Manhattan NY" you'll find a list.
Not sure if you'll find any vintage RL, but it's worth a try.