You can just grab another one from a junkyard, they are interchangeable. Nothing fancy, Its just an antenna that relays the transponder data to the instrument cluster where "PATS" system is located.
If your just trying to see if its working, when you first power it on you should see few hi/lo signals on the RX/TX lines. Easy enough to just connect a led to it. Usually when they die you will not see these signals at all so its a good indicator. This is the pin-out if I remember correctly but you may want to check to be sure.