Not a perfect solution, but luckily the Mixer Surface is (and the surfaces of all the Stageboxes are as well) made of Steel.
So you can just use some magnetic foto papers, like this (dunno if the forum admin accepts that link to Amazon):
Just print the labels you need, cut and place them on the Mixer surface beside your buttons. You
can exchange that at any time fast and without damage. If you have several Sets of Labels, you
can stack “one on top of the other” as well.