Source for gear shift knob threaded insert/reducer

[Tim Ayers]

In this age of Google, I can't believe I'm having such trouble finding a two way threaded insert to put a glass knob on an emergency brake extension.

I need one that is 5/8" 18 pitch OD and 5/16" 24 pitch ID. I've tried so many search word combos, but all that comes up are metric pieces.

Does anyone have a source for these?

Thanks,

Tim