Here's a Batarang design inspired by a wallpaper a friend found online.
For optimum Batarang look, I'd recommend printing it twice and gluing them together (that's what I did for the one in the IRL picture and what is illustrated in the second render).

Dimensions (mm): 193.05×62.5×7mm (or 3.5mm for one face)
Dimensions (imperial): 7⅝×2⁷⁄₁₆×¼in (or ⅛in for one face)

Printed examples using .2mm layer height with a .4mm nozzle, the black ones using Polymaker PolyTerra Charcoal Black, the white one using AmazonBasics PLA White.

Stand for it: https://www.printables.com/model/254241-batarang-stand
 

KO#3

For the inspiration, search for “Chibi Batgirl wallpaper”, you should find it.