I've got several of John's newer releases like "Mail Order Mystics" and "Blues for the Lost Days". I also have a two CD compilation of his stuff from 1969-74. It's released under Polydor's Chronicles series and is called "Room to Move". Has 30 songs on it. Here's a link to it.
I'll check out some of the female vocalists you have mentioned.
KEEP EM' COMING!!!!!!!