I printed the spool holder laying on its side with supports for the filament sensor mounting bracket and the spool holder attachment nibs.

Holes in the back of the filament sensor bracket are for M3 inserts. The sensor stays in place without screwing down. I simply wasn't sure about the fit, so I added the insert holes. And since they were there I used them.

I also included files of just the mounting bracket if anyone wishes to incorporate it in any other design.

Link to sensor on Ancubics site:

https://store.anycubic.com/collections/for-kobra-2-neo/products/filament-runout-sensor

I bought it from Amazon:

https://www.amazon.de/dp/B0BQ2B4RMF?ref=ppx_yo2ov_dt_b_fed_asin_title

Printer settings

Printer: 

Anycubic Kobra 2 Neo

Supports: 

Yes

Resolution:

.2

Infill: 

20% Gyroid

Filament:

PETG