I think you have gotten alot of good advice about the Mandarin. Probably on a fly it would be nearly impossible to tell Mandarin flanks from Woodduck flanks and Mandarins are raised domestically for food and because they are so beautiful. They are available but not really easy to find in the US. If you keep searching for one you will probably find one eventually.

Jay is a bit different story. As you might know, all of our native non-game North American bird species are protected by law and it is illegal to possess them (even if you found one dead on the side of the road). However, there is a Eurasian Jay that is not a North American species and they are offered from time to time in the US. Right now, there are a couple pairs of Jay wings in the US for sale on e-bay. People who deal in Salmon fly tying materials or who import the Cookskill materials into the US might also be able to help you there. Again, it is a bit hard to find but not really super expensive. I think there are some of the Bergman patterns that require JC body. That is pretty tricky to find. A couple want Bittern. I think that one is totally impossible today. Good luck!