This is a very simple but functional case for a DNA250C chip which can be powered by two 26650 batteries. After hours of searching in vain for an existing design, I had to try it myself. For the assembly you need 3 screws size M2 with nuts and spacers as well as 4 battery poles and silicone cable.
The lid holds with 8 neodymium magnets. The holes are 4,2mm x 5,2mm and 4,2mm x 2,2mm.
This is just a prototype and I have not been able to test it with a DNA250C yet. However, the batteries fit very well. According to the data sheet, it would have to fit.