Accessory power cord does not fit with case; one out of the box does

I received my 5s with power cord. It works perfectly fine with both an apple 5s case and a another case I bought at Best Buy. No problem at all. However, I also purchased an extra power cord accessory at the Att dealer and that power cord does NOT fit with the other case. In short, the powercord that came out of the box with the phone fits either case whether an apple case of not. The accessory does not. When I loook at the actual connector, they are different. The one with the accessory is "shorter" that the pne from the box. Therefore, it wil not go all the way in. How do I get extra power cords exactly like the one that came in the box? That one works.