Please be gentle, this ia my first ever upload, and first ever 3D model.
Like many people I use those 4L ceral tubs for my dry boxs. What I needed was a way to join my dry box to my P1S. I looked at many different soloutions before thinking of this.

Designed (if you can call it that) in Tinkercad. Print with a 10mm brim to aid stability.

How it works. I deliberatly made it a snug fit for any 1.75mm filament.

I used a spare PTFE conector from Bambu as my interface. Feed your external filament to the print head and when you finish printing, return the filament to the dry box and insert the filiment and plug yourm box. It is easier to do than explain