Here are providers of Slovak and Eastern European food in the local Washington, DC area, as well as a few online sources.
Markets
Kielbasa Factory
(Polish & European Deli and Grocery)
1073 Rockville Pike (Talbott Center)
Rockville, MD 20852
(240) 453-9090
http://kielbasafactory.com
Products: Kielbasa, pierogi, and other Polish and European specialty goods.
Polka Deli
(Polish Food and Market)
13438 New Hampshire Avenue
Silver Spring, MD 20904
(301) 384-DELI (3354)
https://www.polkadelimd.com
Products: Pierogi, sandwiches (e.g., breaded pork chop), groceries.
European Delight
1488-I Rockville Pike
Rockville, MD 20852
(301) 230-9371
Products: Russian, European, and International food, Cookery, and Delicatessen.
Online
Andy’s Deli
5442 N Milwaukee Avenue
Chicago, IL 60630
https://www.andysdeli.com/online-store-catalog/
https://www.andysdeli.com/product/polish-sheep-cheese-bryndza/
Products: Bryndza, Polish rye bread, poppy seed cake, pierogi, etc.
S&D Polish Deli
2204 Penn Avenue
Pittsburgh, PA 15222
https://www.polishfoodandgifts.com/
Products: Bryndza, pierogi, etc.
Butter Maid Bakery
425 Boardman Canfield Road
Boardman, Ohio 44512
1-844-NUT-ROLL (688-7655)
https://www.buttermaidbakery.com
Products: Kolachi rolls and cookies, and lady locks.
