I've had one of these (https://www.amazon.com/Tempered-Glasstop-Hygrometer-Quality-Importers/dp/B002TOK352/ref=mp_s_a_1_4?ie=UTF8&qid=1547014613&sr=8-4&pi=AC_SX236_SY340_QL65&keywords=humidor&dpPl=1&dpID=41dWPZkYCcL&ref=plSrch) for a few years now and it works pretty well. The hygrometer isn't the best but the box has a good seal. I also have a small tupperdore. If I were to do it again I'd probably just make a bigger tupperdore.

I bought mine from amazon and it has been amazing. I had to make a second divider for it but that's just a preference thing. Here's a link to the one I bought(I think its just the first one that comes up when you search 'humidor'): This is the one

It holds humidity well and only costs $30. I don't know what size you're looking for, but this is a great one