I've exhausted all the local shops, there's not a great selection of this kind of stuff since Ken Sawada shut up shop a few years ago. Which means I'm looking around online, it's a bit of a pain because even with materials that are still fairly commonly used, nowhere seems to have everything in stock. So I'm making bitty wee orders from various places, not ideal when paying for international shipping!
But that's not the real difficulty. There are places where even some of the rarer feathers can be got hold of, unfortunately, when you ask for a CITES certificate the number of vendors dwindles pretty quickly. It should be fairly easy and inexpensive for anyone selling things like domestically produced jungle cock or shed macaw feathers to get a certificate, but I've lost count of how many places revused or just stopped replying when I asked. It's something I think is important though, if we're going to continue use animal products in our flies we need to make sure they're responsibly sourced, and that definitely includes not buying illegally traded wildlife products. It's not just classic materials that are on the CITES list either. You can be sure that if you get an unsolicited message from someone on Facebook their birds aren't going to be captive bred, but you could give them a chance and ask for a certificate. Really though, it doesnt matter where you're buying from it's worth asking for a CITES when buying anything on the list, certainly don't "forget" to ask just because you really like that JC cape. The more of us who ask, the more suppliers will have to make sure the materials are legitimate.
Some people won't care, some people will but still buy the stuff regardless, a few will care and will check the list and ask for a certificate. Hopefully more people will start asking. Especially when books like the Feather Thief are being read as much by non anglers as anglers and people become more aware of flytying, the wrong people findig out about a shipment of poached chatterer destined for a fly shop would be just the kind of thing that would lead to greater restrictions on tying materials. Aside from the impact on the populations of an endagered species and I for one don't want to contribute to that. It's not so onerous to track down feathers from captive bred birds or use subs.
Here's a link to the CITES list. https://checklist.cites.org/#/en
Another interesting project for US residents is the kori bustard conservation programme, you can find out more here https://feathersmc.com/kori-bustard-program/
So there are ways to do it right. But the first thing to do is ask for a cerificate, if we all did, eventually it would become the standard