Alternates to a regular six-string acoustic guitar

Baritone Ukulele - https://en.wikipedia.org/wiki/Ukulele#Types_and_sizes
Tenor Guitar - https://en.wikipedia.org/wiki/Tenor_guitar
Bajo Sexto - https://en.wikipedia.org/wiki/Bajo_sexto
Baritone Guitar - https://en.wikipedia.org/wiki/Baritone_guitar