You might try Craigs list. I've used it with success several times.
I also have some mixed birds. Last year I had a few Bourbon Reds, a SPanish Black Tom and a Blue slate hen.
Some of them turned out Reeds, so I think mom and dad were both Reds.
Some of them turned out Black, so the black was the dad and not sure who mom was.
I also got a few slates, some that looked like real Blue slates and a couple that I call Chocolate slates. The Blue Slate with a redish tinge to the feathers. They look nice.
I also got one tom that I call Stripes. He looks like a Narrangasett. I'm not the gene expert, but seems most of the genes are there, just how they are arranged and which ones are dominant.
THis year I'll put the reds together and keep them for breeding. I'm partial to the reds, liek the temperatment and they taste good. The rest are for eating, either myeslf or others, and no, I don't think it really matters once you take the feathers off them. They are all good.
I'm not trying to create a new breed, just see what looks I can get. Not sure who I'm going to try to cross him with this year. Kind of reminds you of the Mandell Experients with peas from junior high school.