Become a VIP member of TER so you can use the VIP searching function that will allow you to specify a search on "will bring second provider".

Also -- use agencies known for such, e.g., kamasutranyc.com, julienyc.com.

Make sure (if you use an agency) that the two girls you want to select are compatible. Don't just go by your little head on this one.

-Hoot.