Several have been sold but I don't like them. Maybe someone will advise but my thought is find a rod that will just go in with a shoulder. Having the alignment bar inside the coupler for me is a bad idea. Only way this would work out is if the coupler was perfect alignment.
You could measure from the front of the coupler to the rear face of the housing, then subtract another 1/4 inch so there is no way for the alignment tool to start to go in the coupler.
If the bar had a shoulder then no need to drill hole. Or use a bar the right size and then drill hole so bar just goes past bearing
