No idea if they are correct for your application. So sorry if this is usless/egg sucking.
Looks like the fitting common in usa and on trucks (well erf's). Does it have the little ball on top?
They actually work well as the grease gun fitting slides over and locates properly, so you don't make as much mess (usually). They work perpendicular to the fitting, so would do well in your application, ie you work from the side, not underneath.
The adaptor screwed on the end of a normal brit pattern grease gun. I found a flex brake hose which had the same thread, so swapped that for the rigid tube, was much more convenient.
here you go,
http://www.saeproducts.com/button-head- ... tings.html
Lubetech from here, have an adaptor - PK101 amongst others.
http://www.lubetec.co.uk/#/grease-guns/4537937859