I use the KJ COOSWI humidity/temperature sensors, which I like because they use CR2023 batteries and seem to be accurate enough for use in my dry boxes.  I wanted to attach them to the drybox lids so they are at the top and I can easily see them.  You could also attach them to the front if you stack your boxes.  Regardless, I needed a simple bracket to hold the sensor.  I designed this to attach using two small 4 x ½" wood screws through the dry box lid.  It still allows for access to the back so you can replace the battery and use the buttons without having to remove the sensor.

The internal dimensions of the box is 58mm (L) x 42mm (W) x 13mm (H) with 2.5mm thick walls.  The holes for the screws are 2.25mm in diameter and 13mm deep.

I printed this using black PETG on a 0.40mm nozzle at 0.20mm layer height and 3 perimeters to have solid walls, but I don't think that's really necessary.  At these settings, it used 12.36 grams of filament and printed in 26 minutes on my MK4.

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