I've not found many places really, but there are some good fascinator sellers if you search for them on eBay who make feather hair-pieces and veiled top hats and stuff like that, you might want to try
http://www.etsy.com/ too for some original hand-made pieces.
Other than that, here's my main resources:
http://www.whatkatiedid.com/http://www.modemerr.com/index.htmlhttp://www.stopstaringclothing.com/I've lost a lot of my links from last year's infamous computer break-down, but I mainly buy from high-street stores though when they have retro styles, or I buy original vintage from sales and markets and stuff. Good luck! xx