I stumbled upon this wonderful 3D design which is actually printable.
It is an attachment to be clamped on the arm so you can play the piano.
It allows you to arpeggio one octave in the major and minor scales on all of the white and black keys!
A wonderful design if you’d ask me. I think a lot of people would like to have solutions like this.
Now, in case you are not able to print it your self. You can order prints on Thingyverse or if you live close near me (The Netherlands) I can print it for you for just the material and shipping cost.
Be sure to visit Mat Bowtell his Thingiverse page.