How about trying to get one from a scrap yard. That way you can work out what holds the liner up at the rear too. Also it should be the least expensive option. I recently got two front fog lights and the shark fin(off the boot of a cabriolet, so still don't know yet how the liner is dropped)for £20.
Cheers for now
Dave

 

Just remember that the stock antenna is amplified. If you want to actually listen to the radio, you're best bet is to find a used one in good shape.

Otherwise non-amplified ones are pretty cheap. I think I have a new one lying around somewhere...

 

The stubby I bought on GS is not very good. I got lots of static out of mine compared to my OEM one, so I switched back to stock.