While far from the cheapest option, Whiting 100 packs and saddles are all I use.
As far as size goes, because 99-9/10% of people gauge hackle based on hook gape on a BARE hook shank, if you are winding hackle over a body like you would on an Elk Wing Caddis, the hackle tips end up further away from the body than they would would would on a bare hook.
In other words, any time you wind sized hackle over a material it appears bigger. For that reason I typically use one size smaller, so for example I use size 18 Whiting 100 pack hackle on size 16 flies.
Another hackle option you can explore if you do eBay is
Bill Skilton. I believe Bill is raising chickens for hackle and sells feathers and other stuff on eBay.
Bill is a stand-up guy who lives in Boiling Springs and he's an excellent fly tier. I've bought a few things from him via eBay over the years.
You can reach out to him through eBay and tell him what you are after and I'm sure he'd be glad to help you. If you don't do eBay, PM me and I can give you contact info.