As our cars are aging, the many pieces of plastic are becoming brittle. Last year when looking for a 6 speed, I noticed a few of them had the shifter boots loose from the console. They would snap back in place, but once putting them in reverse, the boot would pop up again. Mine started to do this once I changed it over to an aftermarket shifter. I noticed that one of the 4 tabs of the boot retainer was broke off. The retainer, as far as I know is not available separate, and comes with the boot which impossible to find as well. Today I took some time and solved my issue. Very easy for anyone with this problem. The missing tab is in the yellow circle.



A small piece of metal bent 90° and a 1/8" pop rivet.

 

I bet an intrepid soul with lots of time could create a 3D print of the retaining ring - maybe with modified/extended tabs for better securement? I know some printers can use various types of "springy" plastics like ABS, nylon, etc.