I joined the Addi express and circular knitting machines Facebook group and recently someone posted that you could buy the king-size version for almost 70% off on Amazon. So I decided to buy one! It arrived and so far I have made a hat and an ear warmer and it seems to work great. I hope to make many more things soon.
NoNeedleKnitting.com 
Is the Addi version still available at that price? I only see a slightly different version with 48 slots on Amazon – https://amzn.to/3Eu8Ldy