Obviously u don't want to print a link to my Thingiverse profile but here's the link to create your own QR codes. It even downloads as an STL for easy creation of your own items.

https://printer.tools/qrcode2stl/

Pic with paper towel and paint is how I added black paint after spray paint the entire item white so that the QR code would work. Tried sponge brush too, to me the paper towel worked better and used less paint.