Morning all.
Quite a few years ago I looked into the poor quality of the standard versions of this bush, and drew up a replacement in CAD. A forum member had some machined up in teflon and I've had one fitted to my bus since early 2019. It far improved the shifting.
Here's a thread I set up not long after I fitted it, unfortunately the drawing I posted doesn't seem to work for me anymore but I'll have a dig around on my PC to see if I have the native.
Thread 'Front shift rod bush - Teflon'
https://earlybay.com/threads/front-shift-rod-bush-teflon.78292/
Two things were considered in the improvement, contact area and clearances. The design used a tightly controlled outside diameter which removed the need to barb and slot the bush increasing the contact area. The bush would compress radially when installed, holding it in place once fully inserted.
If I can find the original drawing it might be cost effective to look at having a couple machined up, check everything fits as it should (a few more testers) then do a group run on them.
Id expect the cost to be far less than these are.
Original PDF found, see attached.