Step 1: Items you'll need.
Cheap set of usb powered speakers
Some wire, I used a RJ45 LAN network wire, and the excess from cutting the speaker wire down.
Portable backup battery supply, mine is a 16,000mAH, with 5 usb ports.
Thin cover material, such as a bottom of a dresser drawer.
And a case, I used a case from a cheap dremel tool, I had got for free.