Here is another possibility that might work. It is an extended length LockNLube coupler.
LockNLube Grease Coupler XL | LockNLube
It is 2 inches longer than the standard LockNLube. I think the technique would be to insert it with the locking lever to the front or to the rear from either the right or left side.
LockNLube Grease Coupler XL | LockNLube
It is 2 inches longer than the standard LockNLube. I think the technique would be to insert it with the locking lever to the front or to the rear from either the right or left side.