Remix or Yanev's model. I've removed the MicroUSB hole, fixed the screw holes and most importantly, I've removed the big slot to see the charge percent and replaced it with small 1.5mm holes to add a transparent acrylic rod for the LEDs.
UPDATE: I've added a variant with an additional fifth hole for the fast charging blue LED that sits between the USB-C and one of the USB-A
Things you'll need:
Included are models for 3 to 8 batteries in a row.
If you need something else, download the f3d file, modify the user vars and increase the size to accommodate more cells. Just multiply 18mm by the number of cells you want to use.
The author remixed this model.