Just a suggestion that might not work out.
There is a young lady in Salem Oregon named Stephanie Andreus. She's quite talented, and has worked on a song for me, and she's adept at both pretty ballads and rap. If a female rap voice would work, you might do an internet search for
reverbnation.com + andreus + oregon
If you go to her site, the song we worked together on was "Cannibals and Lovers." I wrote the lyric, and she independently wrote and recorded the music and vocal. Music is all hers, and some of the lyric is hers. Tell her HardTwistMusic recommended her, and mention the Cannibals and Lovers song if you think she would work to collaborate with. I have no idea if she'd even be interested, but she does have the talent.