Just buy some very cheaply-available electronic price tags [1] and use open-source firmware[2] which supports greyscale + yellow. Save literally HUNDREDS of dollars/euros/etc. For extra credit, they are not only black and white eInk screens, they are BWY, so they can add a splash of yellow!
And, separate question, but I tried just scanning [2] and I'm having trouble understanding how to determine the resolution of the tags in [1].