That's a Universal Z collet. I use them in my mill.
Pick up an organizer from Horror Freight and fill it with Ebay collects. If they're clean and free from burs you're good to go. Those things are available in all kinds of common and weirdo sizes.

Again, I'd skip the VFD and go with a rotary converter. It's a big quality of life improvement.

We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon