I have a laser cut drawing for a box to hold an Arduino Mega with RAMPS 1.4 stepper motor control board in 3mm acrylic, as are commonly used on 3D printers and GRBL systems.
This box does not include vents or fan mounts (yet). You can add these yourself to match your cooling system.

You will need to cut two copies of this drawing for a full 6-sided box. You can delete any mounting/access holes that you do not want in one of the copies. e.g. Cut one copy as is for power, USB, reset, and Arduino mount holes. Make another copy of the drawing to cut with all holes deleted for the opposing plate.

The source code starts with https://github.com/Mr-What/kossel/blob/master/boxRAMPS200x200.pl

The following drawing is for mounting hardware and vent holes to place a gamma28 blower motor on the RAMPS1.4 box for cooling.