I have been using the eBox for a while. It is not a good product and has plenty of issues, but since it was not cheap, I am trying to make it work. This was to say that if you don't have it, you should probably look for a different product.
Anyway, one of the issues is that eSun has not added a hygrometer, and I would like to have an idea if the dessicant is still effective or needs replacement. I have a bunch of hygrometers, which cost just over a couple of dollars on AliExpress (see this one for example).
This support allows you to put the hygrometer inside the eBox, next to the spool, and easily get the humidity inside the box. All in all the box keep moisture out decently, if the dessicant is fresh (mine was obviously not when I took the photo).
I have included the Fusion 360 file.
Aug 8, 2019
Added v2: changed the feet shape for a better fit inside the box.