In differences from other containers with hygrometer i have seen, this's lid allowes You to attach hygrometer without need of useing a glue and the container is overall prety much rigid, which is fine when i dry them, they doesn't deform due to heat.

Appropriate heights for different spool widths
(heights are with hygrometer included – +2mm)
55mm for 0.5kg & 0.75kg spools
65mm for 0.75kg & 1kg spools
75mm for 1kg spools

Releasing the hygrometer from the lid is tricky, but possible. Stick flat and narrow tool into lid's groove (inside the lid, above the thread) and push it away while levering the hygrometer's anti sliding protrusions inside. Attention! Do not harm Yourself while performing so, if You use for instance flat screwdriver, and push it hard against the lid while holding both in Your hands, You might stick the screwdriver into Your hand and harm Yourself badly!

Links below include offers that have been most cost efficient in time i have been looking for such goods in country i live in (Czech Republic). So they might not be the best options for everyone.

Hygrometers (doesn't include batteries)
https://www.aliexpress.com/item/4000411680225.html?spm=a2g0o.9042311.0.0.27424c4daavw3O

Batteries
https://www.aliexpress.com/item/32966748359.html?spm=a2g0o.9042311.0.0.27424c4dLHi4ug

Silica Gel
https://www.traiva-shop.cz/bezpecnostni/pri-praci/4835-silikagel-sg5-ciry/17890/

Silica Gel with indicator
https://www.traiva-shop.cz/bezpecnostni/pri-praci/5492-silikagel-so1-oranzovy-s-indikatorem-vlhkosti/17895/

I hope You will find my remix useful. I will be glad, if You press the like button for me. Thank You and Happy printing!