As you will visit any provincial of Cambodia, at Battambang, you can buy most commodity at every market located near center of town, even though small towns.
Phsar Nath is in the centre of town is the main Phsar (traditional market) and is geared to the locals, sporting the usual variety of fruits, vegetables, meat, clothes, sundries, food stalls, etc.
If you are finding a photo shops and money changers line the streets that ring the Phsar. Phsar Leu, just south of town, seems to be the place to buy the local specialties: oranges and pomelos from Pursat province. The oranges are said to be the best oranges in the country. Many small Drink Shop on the west side of Phsar Nath offers ice cream bars, cheeses, yogurt, wines, and other imported items.