You can find lotus root at most Chinese (and Asian) markets. In Honolulu, we usually purchase lotus root from one of the many mom and pop shops in Honolulu's Chinatown. We also buy lotus root from Nijiya in Ala Moana Shopping Center - Nijiya is a little more expensive than the Chinatown options, but it's more convenient (free and easy parking), and they also sell pre-peeled lotus root.