I've seen mass-produced ones in various shapes. For instance, stars. OP probably could, not especially complicated.

Notably worse at the act of 'slinking'. Would tangle like no other!

Yes haha exactly. I'm sure I could figure out the code to slinkify any object which would be pretty fun

For a non-circle that still works for slinky purposes, I'm sure some sort of geometric prism would be cool. Maybe I'll take a crack at it over winter break!