Whole Foods does. There's also bulk grain stores most everywhere there's "regular" grocery stores, but of course far fewer because there's little demand for such. Bulk goods also trivial to buy online.
I honestly never thought to try online just because I was worried about food safety during shipment. I could try Whole Foods but everything I've bought there in the past has been massively overpriced. I haven't shopped there since Amazon acquired them though, our local chain has been fine for most of my needs, besides bulk goods.