I have a stylophone. It's not easy to tape the stylus in place, so when I've used it as a drone when playing a recorder I've simply held it between my toes.

"a curious solution to a particular problem which introduces different modal possibilities without compromising the essential purity of the diatonic / Phythagorean scale. In many of these diatonic board zithers, the Swedish Hummel in particular, the melodies are traditionally played by harmonising in thirds against the open drone strings"

Sedayne, you don't know what the Pythagorean scale is. It makes fourths and fifths pure - thirds and sixths sound worse than they do in the equally tempered scale. You are thinking of either just intonation or some version of meantone, which are entirely different.