This is based on a project from Thingiverse:

https://www.thingiverse.com/thing:1631545

I hollowed out the back and created a channel to insert LEDs into the design, which I think you'll agree is a big improvement. This was printed at 250% to fit on my rather large Folgertech FT-5 printer, making it 25cm wide and around 29cm tall.

The LEDs used were from Amazon, below, but any sort of LED would work.

https://www.amazon.com/gp/product/B06X9PK3FK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I hollowed out the inside in the back so it would use less filament, AND so you can pretty much stick anything in there. The LEDs above come with glue on them so it was a snap to make it adhere to the plastic. Other LED sets might have more ascetically pleasing blink patterns or colors, so try anything you like.