Case for Cheap USB/Bluetooth MP3/FM Player

This DIY project uses a cheap Mp3/FM player and two speakers to build a small soud system.
The system is powered with one Li-ion rechargeable battery, connected to a TP4056 charger module; so it also works with an USB cable and a cell phone charger.
The system uses a XL6009 step-up voltage regulator, to proportionate a steadier input voltage for the system.
- The suggested output voltage in the XL6009 should be 12V, but it may differ from a model to another.
- In the 5th picture above, its shown how I calibrated the output voltage in it.
The player's case is a modification from this thing: https://www.thingiverse.com/thing:4942179 .
The speaker's case is also available here: https://www.thingiverse.com/thing:7291429 .

Parts Needed

2x 3W rectangular speakers - 65mm x 35 mm (2.56" x 1.38"). See pictures above.
1x cheap MP3 Bluetooth FM player (with amplifyers) - small version. Easily found on AliExpres (and in many other gadget stores).
1x Li-Ion (or Li-Po) lithium battery.
1x TP4056 charger for lithium batteries.
1x XL6009 step-up voltage regulator.
1x KCD10-101 rocker switch (20mm x 15mm).
10x screws.
Wires.
Double-sided tape.