From my experience, only Prusament rolls fit properly in the grooves under the Mini. And even then, it doesn't turn super smoothly.
I made this lazy Suzanne so that I can use it with any filament brand, no matter how wide the center hole is (Hello Eono with your massive 10cm center holes!)
I designed it to only require parts from the Mini's spare bag so there is no need to wait 3 months for that Aliexpress order to arrive: it uses a 608Z bearing (from the original filament spool holder that came with the printer), a 12mm M3 screw (look in your spares bag), and an M3 nut (either Nylock or just the plain, slimmer variety).
I added little hexagons all over the tray to save on plastic and keep with the Prusa theme from the Mini base.
Note that for the tray and for the axis, I am using a sacrificial layer so that the holes print well without needing supports. Once the print is done, simply punch the layer obstructing the screw holes (either with an allen key, a screw, or an exacto knife).
As usual, STEP files included for easier remixes.
I recommend using the supplied 3mf file as it contains the correct settings and orientation for optimal printing.
The author hasn't provided the model origin yet.