Dave
The fix used by several manufacturers back in the day for inaccessible grease nipples was to remove the grease nipple during service and fit a longer one (these used to be available about 1.5" long. After the grease the nipple MUST be changed back as the angle of the yokes would shear it off.
Some cars even had screw slot blanking plugs where there was not even room for a short nipple. Sounds a faff but in reality takes seconds and as you can image a few pence compared to a new grease gun or fancy end piece. I am sure someone somewhere would have stock and with a 1/4 drive small socket could be a useful addition to your kit.
