http://vrici.lojban.org/~cowan/tiresias.html
Gender bender erotica written thirty years ago by John Cowan, now the chair of R7RS-large. Tragically, it descends into hetero, but you can just read the first couple sections for the yuri stuff. He manages a few good lines, but the staccato writing style and the general lack of sensuality make it hard to imagine anyone actually getting off to the story.