I bought a cheap CD case, ripped out the interior CD pockets, and glued Velcro straps on the interior surface. Adhesive Velcro on the back side of the gadgets make for a configurable layout:

The case conveniently opens like a book for easy access to the components. Zipped close it becomes a compact bag that protects the interior:

Attaching a shoulder strap results in a relatively discrete wearable computer: