Build a custom Arduino case sized to the real board. SliceFoundry's enclosure builder covers Uno R3 and R4, Nano / Nano Every / Nano ESP32, Mega 2560, Leonardo, Micro, Due, GIGA R1, and Portenta H7 - with ports and holes locked to Eagle CAD and OEM STEP sources.
Toggle USB and DC jack openings, confirm millimeter fit, optionally engrave a lid label, then export print-ready STL. Same tool makers use for Raspberry Pi and ESP32 cases.