I would suggest contacting Jade and Kit of desertdelights.  They are well know for their great two girl dates.  I've seen them together twice and solo numerous times.   Jade is retiring in June so if you've never been delighted, best to do so before she is gone.  Another option is CindySpice and Jackie Jewel.  I've never seen  them together, but will some day.  Both are real nice ladies and real good at what they do.  Beyond that I would suggest contact ladies you are interested in and ask them if there is a lady that they like to work with.   Logan, Celtic Lass, Tia, and Roxy I'm pretty sure all work in threesome.  I'm sure there are others out there as well, just need to do some digging.