Ah. I get it.
Well, you simply need to generate a QR code containing the appropriate login URL, which would be in the form
How exactly do you generate this QR code depends on the rest of your setup.
In the video above for example, it seems
like both the number pad and the printer were (wirelessly, of course: show offs...) connected to a computer off screen, where a program of some sort was receiving input from the number pad, and was responsible for generating the QR code that is then printed along with the actual site, username and password (for those who don't have QR code scanners on their phones/computers).
Which program to choose exactly is somewhat subjective. There's a free python generator, but not only does that mean that you'll need the Python runtime, it also means you'll need an additional program to then take that image, and combine it with a text. Oh, and that same program should probably be responsible for generating the random username and password to begin with. I'm unaware of any "off the shelf" solutions to THAT part.