where can i buy fresh lettuce, carrots, etc near Taipei Main Station?

Are there any shops selling these near there, or do I have to find a real market?

Well there is Jason’s supermarket in the basement of QSquare, the bus station next to Main Station. And Tianhou, the organic supermarket is a couple of blocks away. Even Mitsukoshi, across from Mai Station, has a supermarket.

There are several small fruit shops on BoAi Road, but those are high end.

Closest traditional market is Chengzhong, on Wuchang road.

EDIT:
Forgot about Zhongshan Market, on Chang An road and Zhongshan intersection. It has plenty of fresh veggies and meats.