$10 mouse feet seems... excessive. I'm sure you could buy the material and cut it yourself somehow.
You can not cut the material to this shape without some sort of manual polishing process.
It's not just the outer edge shape which makes the hyperglides smooth, It's this bowl shape contour in the z-axis from the convex punching.
I also don't see virgin teflon sheets on ebay.
The ones from China, that would make this project "within a reasonable budget" are mechanical grade teflon.. It is smooth for the most part, but it's harder and not as soft as virgin grade teflon.
It may be posssssible to get to this shape and quality on your own, But not without a labor input well exceeding $10..