Thanks so much @kage-chan (and @PinkLightning) for your replies, I really appreciate it.
The PCB spacer tube is a great idea and sort of what I went with. I did think about using a 3D printed part, but I don’t have convenient access to a printer.
I went with something similar to your idea that I came across in another forum. Using some Brass Thread Inserts (www amazon com/gp/product/B07MWBJB67/r), I was able to heat them up with a soldering iron and embed them into the plastic (after trimming off the jagged pieces).
I added some hot glue to around the base of the inserts for some added support. On the bottom one I initially added too much glue and the glue kept the insert from fitting into the controller properly. After trimming the glue back and trying again things fit fine.
Not sure if it was worth the trouble though… the controller isn’t that great overall. Is fun to use for games like Twin Bee and Xevious though :-).