I have bought diy led heart kit and decided to create a case for it. 

I also added li-ion battery so it can be used without external power.

Disclaimer:

This device has li-ion battery and requires skills in electronics, so make sure that you have necessary knowledge and take all safety measures. Author is not responsible for any possible damage.

Parts List:

• DIY Led Heart Kit
• TP4056 micro usb charger with built in Step-Up.
  • Don't forget to change current set resistor to appropriate value for selected battery.
  • Don't forget to set step-up output to 5 Volts
• 100mAh 302040 (30x20x4mm) Li-Ion battery with BMS

Note: I haven't provided any references, but all parts can be easily found on aliexpress, ebay etc.

Printing Material:

I've used Eryone 3 color silk pla with default bambulab settings. But any material can be used.

I also used fuzzy skin mode for case, which looks gorgeous.

Printing and assembly notes:

1.  There's a thin wall in front of USB port in “case” model, which is necessary to better printing. It should be cut out after print.
2. Mid plane model is used just to isolate pcb and battery. Make sure that you've installed it before soldering power wires.
3. I found that step-up consumes 0.1mA even without load. So I cut traces on tp4056 module and under the button on Led Heart's PCB (see photo). So, button is also used to connect battery and step-up. But if you're ok with such current drain, you can skip this step.
4. When installing diy led heart pcb make sure that you haven't pushed it to far, so button is working without issues.
5. I used hot glue to fix parts inside and supper glue to fix lid.