Here's my collection of knobs for the Teenage Engineering PO-400 Pocket Operator.

The knobs from TE are all standardized, so they also fit the KO II.
I'd advise against printing too many at once on the A1, or to properly configure the bed adhesion settings. Currently the profile prints the first layer at 10 mm/s, but even that sometimes causes issues.
The ones in the pictures were printed with AMS.

If you want to create your own knobs, I've built a website where you can freely design your own knob with any shaft opening (TE style or regular synth style) and export the whole thing as an STL. Have fun with it!

[https://janschulten.github.io/Online-Knob-Creator/](https://janschulten.github.io/Online-Knob-Creator/)