For oddball labels like the QR Code, I use a company called OnlineLabels. You can get almost any size/shape label made from any material they carry. I tend to use the weatherproof polyester labels for asset tagging, since they hold up to abuse and exposure a lot better (OL1502LP). As for a label printer, I've never had much luck with them because the drivers for them are often finicky and poorly written. Zebra printers, for example, have effectively neutered drivers for the hardware straight from the manufacturer. Seagull Technologies has written an entire library of drivers for Zebra hardware that actually corresponds to the hardware's capabilities, and are often required in place of the Zebra drivers for some software to even use the printers.
The QR codes can generate in a HUGE range of pixel sizes in lansweeper, but remember that pixel size only determines clarity when printing. The more pixels, the sharper the image at any given print size. Since QR codes are simply b/w squares in a 2d error check pattern, the image resolution doesn't have to be very high for an effective read.