I was getting by with some castoff feathers from gulls and crows (ravens?) down by Golden Gardens beach nearby, but I realized I needed something a bit more colorful because I kept losing the darn arrows in the forest.
So, went to the local arts-and-crafts shop and got some "craft feathers". They are turkey quills, plenty strong enough for good vanes, and brightly colored enough so that I will hopefully lose fewer arrows in the leaf litter. Cheap enough, too.
Added bonus, no worries about grabbing feathers that the government says I shouldn't pick up from the ground.
Goofy looking bright colors, but considering how fast I destroy/lose arrows, I'll only regret the colors for a little while before the arrows are lost.