Aquila Corde make a set of strings for soprano sized (i.e. ~ 13 inch, more or less the same scale length as a violin) for tuning in fifths. I have just bought a set over the web from the company and plan to build a soprano with a narrow neck and a few other minor adaptations to use them. I am used to playing and reading music for violin, viola and bass (my bass is tuned in fifths too) so hope to be able to play any treble clef music onto this new instrument - mostly tunes, rarely chords.