I don't have one for sale , but I've seen plenty of 203's with towbars in breakers yards . If you are lucky you'll get the electrical modules as well . Not sure where you are , but I've seen three recently ( two estates and one saloon ) in the Glasgow area .
I have in the past paid around £25 for a basic Witter type fixed flange bar ; I would expect to pay more for a detachable one , but still a lot less than dealers would ask .
Removal/fitting is a very easy DIY job since all mounting points are pre existing .
EBay can also be good for sourcing a used bar , but I prefer to take them off cars myself so that I get all the nuts/bolts/ washers as required