I can usually buy it fresh at Viet Hoa Supermarket, 5810 W. Alameda Ave., Lakewood, CO 80226, tel. 303-975-9900. I can always buy it frozen at Kroger/City Market.
I've bought frozen in any grocery store I've ever tried to buy it at. Fresh I've never worked with but have seen it at regular groceries on occasion, I assume during season but I haven't a clue when that is.