Here are a few versions of my replacement design of a film canister and a petling.
Usual bottle caps like the ones from glas or PET softdrink bottles should fit the container.

I use them with or without magnetic attachments.
The small magnets I use are 10mm in diameter and 2mm or 2x 1.7mm thick.

I use the same plastic glue, I use to stick PLA prints together, to fix the magnets in their according pockets, otherwise they might drop out again.

When the container will be exposed to a lot of rain etc., I cover the container with a layer of clear carpaint spray before placing it.

For the 55mm container I use such a logbook: https://www.marcelcuvelier.de/wp-content/uploads/2019/09/logbuch55mm.pdf