I was able to order starter crumbles for my ducklings from the hatchery from which I bought them - Meyer Hatchery. That worked out fine. They also have gro-gel and vitamins, which are things I like to have on hand for babes (especially the gro gel) and adult ducks as well.
I know someone who orders organic feed online, but don't remember the place. Perhaps you can search BYC for some of our earlier discussions of preferred feeds, and then find a place where you can order that from.
I have to go two towns away for my feed and supplies, so I stock up when I make my trips out. I also keep a few metal garbage cans with tight lids in my basement (which has moderate to low humidity and cool temperatures and no noticeable mold or mildew) for storing fifty pound sacks of feed.
Meanwhile, online there is an article I like from Mother Earth News about growing your own feed. Now, if you don't have the space or inclination, it is still a good article because it lists foods that will nourish your flock, which might be easier to come by where you are. So I'd give it a look.