i’m pretty sure humidors use cedar inside to regulate the humidity. you could build your own wooden ‘humidor’ – i used to know a guy that kept vacuum sealed pounds in the freezer for long term storage
are those just hygrometers? i ordered a bunch of these on amazon for like $1 each
The cheap hygrometers boast an accuracy of +/- 5%, which could mean the difference between poorly cured buds, nicely cured buds and moldy buds, depending on which way the hygrometer swings and what your target is.
better than the nothing i’m using right now at least, my drawer seems to keep the jars at the perfect RH anyways, and i can put 2 in each jar 
2 in each jar might be a good idea.
What I did was “invest” $30 into a quality hygrometer with 1% accuracy, and I switch it between jars as I am winding down my drying and moving into curing. It is a bit of work to check RH and switch it to other jars a few times per day, but slowly I dial down the humidity in all the jars till they hold 62% or less for a full 24 hours. Then I check them every couple days just to make sure. Once I get them all in the zone. I cap them and put them away for a month.
I’d love to have 5 or 6 of the ones I have. Maybe over time I will accumulate them. I will likely buy at least one more before my next harvest.
