Search on ebay (or other car part sites) as I am about to do for my 2005 Santa Fe - i am also in NYC facing the same issue.
Once in ebay...read description carefully to read legal for NY, 49-state, etc; make sure it is direct-fit and comes with gaskets. I advise you email the seller first to advise.
Which one do you want? The car should have 3 - two upfront and one rear. if front ones, chances are you need both.
Now something else: what about O2 sensors? You may need them too; they work together with cats and may be damaged too. Get your mechanic to check and confirm as I am not sure about this. But you don't want to fix the cats then the CEL comes on again when the OBD detects bad sensors. [it won't be fun paying labor twice for this again - better do it once].
Lastly...you may need to work extra hours to cover the cost of the fix