I was curious myself, and shocked to discover that they don't show up in a search on the Pathfinder Wiki...
things that only show up in adventures are more or less the last things added to the wiki... many of the contributors are either players or DMs, most of the time they will read the adventures last, not to spoil it for themselves. This causes Items found only in the adventure paths to get the last write-up. Of course the wiki is also edit-able by anyone... so if someone wants to make a gray maiden entry article feel free!
I really hope that the Gray Maidens lived on some how after the adventure path, they seem too cool to let just vanish off in the wind.
You could always roll them into the Hellknights as some sort of ELITE women-only unit. I'm certain they're lawful, most military units are due to rigorous training and daily beatings, despite possibly being lead by a chaotic individual.
EDIT: Oh yea, almost forgot... NICE LOOKING MINI! :)