Market: Hankook Supermarket
City: Sunnyvale, CA

Can actually be found at most Korean supermarkets. There’s also Super Kyo-Po in Santa Clara, CA and Koreana Plaza in Oakland, CA.

Yujacha or yuja cha (citron tea) is a traditional Korean tea (herbal tea) made from citron. Yuja (유자) fruit is thinly sliced with its peel and combined with honey or sugar, prepared as fruit preserves. The fruit is so prepared because of its otherwise sour and somewhat bitter taste. To prepare as a beverage, a tablespoon of yucheong (유청, thick, yellow syrupy yuja) is stirred into a cup of (usually) hot water. Yujacha is used as a herbal remedy for the common cold and similar winter illnesses. (Wikipedia)