240L loader grease fitting

[6sunset6]

I went to put a shot of grease in the loader arms and the snap on fitting at the end of my grease gun hose will not fit in the recess the fitting is set in. I have not changed that fitting in 40 years. I guess fittings in a recess are a good thing , don't get snapped off but now I have to go find a new end.
Anyone one have a clue so I don't bring home the wrong one the first time. Could get a kit I guess but will probably never use the rest of them.