I have seen them in past years around this time at the Whole Foods in White Plains. In fact, i know that they had some last year, so it might be worth giving the store a call to see if they have some now or will be getting them in.
I'm in the UWS Fairway often and have only seen the Buddha's Hand once this season so far, some time ago now. If it does you any good, though, they seem to be getting multiple shipments of etrog-type citrons - I've seen those several times now.
I saw them today at Fairway in Pelham at $7.99 lb. but they were old, bruised, and beaten up. So I didn't get any and ordered them online. But I did get sweet limes, bitter oranges, and several kumquat hybrids, lime, lemon, etc. from Fairway.