Original Campagnolo pump head for standard square shaped connections. This spare part can be found in Campagnolo catalogues under the code 1030/2 as a "Pump connector with M9 x 1,25 locking screw".

If your vintage frame pump doesn't hold air pressure any more, it may be due to the pump head which is not tight any more. Most of the time it is the rubber sealing which can be just too old. You can replace the whole head for this high quality Campagnolo one, which is made of chromed steel and where the rubber parts are as fresh as if they were new.