where can i buy a travel card for the bus and subway in Beijing is called yika tong

You can buy the card at the ticket offices of all Beijing metro stations (05:30~23:00), some bus stations and some supermarkets, such as Jingkelong Convenience Stores, Lianhua Quick, Good Neighbor Supermarket). Besides, some Post Offices have such cards, open from 09:00 to 17:00. As for the specific locations, you can search out in this website.