I created a version of the filament spool cover with a built-in hygrometer that will allow you to constantly monitor humidity and temperature values.
The hygrometer housing hole may be a little narrow, but I preferred to leave it like this to minimize contamination with the atmosphere outside the cover. You can always widen it in post-production with a deburr. To improve the airtightness, I added a small TPU gasket placed between the hygrometer flange and the cover surface. In my opinion, the final result is satisfactory, however if you think this solution is not very effective you can seal everything with a small layer of silicone sealant.
Among the print files you will also find a key that will help you unscrew the half-shell with integrated hygrometer which obviously will no longer have a handle, if you think you don't need it, obviously don't print it.
The new half-shell is perfectly compatible with the previous version so you can decide to print only the one to update your spools, however in the print file I have inserted all the components to create a complete cover.
To facilitate assembly I created a kit consisting of a support base and a flange with a hammer function, you decide if it can be useful to you, I have however added them to the list of shared files.

ATTENTION!!!
The gasket printing plate contains 10 pieces, in reality one is enough, I thought it more logical to print several pieces at the same time rather than one at a time, if you don't agree with my thoughts, exclude from the print the pieces you think are redundant.

The hygrometer used has the following measurements:
body = Ø41 mm
Flange= Ø45 mm
overall height = 16 mm

Below is the link to the product used:
https://it.aliexpress.com/item/1005004676231259.html?spm=a2g0o.productlist.main.29.55a3dPX4dPX4CJ&algo_pvid=9f2f6c3e-2444-4e23-b30f-64a7148d0ef7&aem_p4p_detail=202311171041193260763705217850001178643&algo_exp_id=9f2f6c3e-2444-4e23-b30f-64a7148d0ef7-14&pdp_npi=4%40dis%21EUR%214.62%212.72%21%21%214.90%21%21%40210385a817002464791886084e25ec%2112000030065550328%21sea%21IT%210%21AB&curPageLogUid=KBniZJOTIsJw&search_p4p_id=202311171041193260763705217850001178643_15

Attention!!! The new cover is compatible with all coils that have a hole larger than 54mm.

Please forgive the English, but I am using Google Translate for the translation.

Happy printing everyone!