If you need that much feed, surely it would be cheaper to buy the powder and mix it up yourself?
It's not too hard - just work out how much powder you need and mix that by hand into a bucket of feed. Then get a friend to mix that bucket full into a feed bin as you add the main bulk of the feed simultaneously. It's hard to mix a big bin of course, but if you're able to transfer it from bin to bin and mix as you go, it should all get evenly distributed?