Hey Campagnolo minutiaists! I just realized I have two different "Sport" single pulley derailleurs in my junk box - one has the parallelogram pinged together in four places, and the other has three pings and a threaded screw in the lower pivot closest to the pulley cage, allowing you to disassemble that pivot (for cleaning, perhaps?).
Check your collections - you might need to go on eBay tonight after all!
If this is old news, please ignore this message.
Aldo Ross
Middletown, Ohio