It might also be good to know that, in Korea, a large number of the beans are sourced from Ethiopia and other parts of Africa. The flavor tends to be more acidic and bitter than you will be used to if you generally drink beans from Central America. It's not bad, it's just different. You also really need to keep it air tight so that it doesn't get too intense.
That said, you can get single source beans from a few of these roasters. For example, Cafe Kong has the most choices from Central America. We often use them since we prefer softer, smoother coffee.
Since pricing also vary a great deal based on bean source and market prices, we have not included prices.
All that said, here are our favs:
1. Cafe Clark: In Bijeondong
Address: 경기도 평택시 평택3로 83
2. Coffee Kong: Near Songtan
Address: 경기도 평택시 장당동 635-4
3. Gabae Maru: Near New Core
Address: 경기도 평택시 비전동 838-5
4. Coffee On: Near AK Plaza
경기도 평택시 평택동 65-23