The Amp HAT Case is a suitable enclosure for the Raspberry Pi and Amp HAT.
The 2 piece case is easy to use and protects the devices.

JustBoom Digi HAT is available here at RS (RS 1228183).

For guide see URL : https://www.justboom.co/start/set-up-justboom-amp-hat-and-case/
Features:
•Supports and protects your JustBoom Amp and Raspberry Pi
•Easy to open case allows for quick access to your Amp and Raspberry Pi boards
•Smooth black finish that blends in with any audio setup
•Leaves all ports accessible
•Compatible with the Raspberry Pi 3, 2, and B+
•No tools are needed for assembly or disassembly
•Designed and made in the UK from high quality material
•4 x rubber feet included
•Access to micro-SD port