This refill spool ist fully parametric, created with FreeCad 1.0.2. Feel free to adapt to your own needs. Given dimensions are for refill spools from the “Recycling Fabrik” https://www.recyclingfabrik.com

Sides can be created with a lasercutter instead of printed 3D (use sides.svg).

In addition, you need two long M5 screws incl. two nuts.