My new favourite search term on the Net is "fly fishing shops". They contain a whole new world of feathers that I never knew existed and had never considered until recently.
It came as something of a mild shock to discover that I can also buy dyed squirrel tails, bird wings and sometimes even complete bodies. I don't want to though, I'm too squeamish for that.
To take a look at what I'm talking about (feathers, not the squeamish stuff) then just take a look here. Prices are a little breath-taking, but ooooh, aren't they pretty? And, yes, I've looked at shops in the UK too but there's no-one in the UK that has a range like this.