Here is a form to get in touch with the organizer.
That way he can organize what flies he needs. He is offering to match flies donated with his own. I offered a few sizes and flies and he got back to me saying which would be best for his groups.
As Ard mentioned, there may be a group that is operating much more locally to wherever you are. Might be worth following Ard's link on the original post to help out local organizations.
I am tying 'purple heart rainbow warriors', thought it was fitting!