Costco used to sell a large-ish plastic container that had a nice mix of various dried mushrooms, including shitakes. Then they sold a smaller container with only sliced shitakes, but those (by Shiitake-Ya) were recalled because of a possible fungicide contamination.
I haven't been able to find anything similar since then. The Asian markets sell only huge bags of dried shitake mushrooms, or I can get those very little containers - I think they're dried porcinis.
I use them to give my mushroom soup a more intense flavor.