There are quite a few breeders with those, they species the others listed, you're not gone find, very few ever come available outside of zoos, and specailist breeders, and they are all in their own little bird click, so you'll never see then for sale.
Look in the Gazette and A.P.W.S., also the GBWF for sale site, also
a few breeders on here with them, chickenzoo, just got some of this years on the east african.
Sid Drenth,
www.texaspeafowl.com has them. Doug McNutt has them (DMFarms on here)
The east african are about the most common seen for sell. Yearlings are about $1500 pr, give or take a few hundred.
If you dont come across any from there, PM me, I'll get you some more detailed info on breeders.
as for mixing, never had any myself, but have seen demoiselle in mixed waterfowl collections a lot.