Sorry, I can't really help you there. The only thing you can do I guess is find such speakers in reality as a conversation partner - similar to what many universities offer to foreign students to improve their English. This way you could improve your "funny"-English skills
(no offence to any non-native speakers I am one myself).
I know we have authentic texts on the CDs that come along with our student books, meaning if we have a text about Africa it'll be an African person with an African slang reading the text. If it's about India it'll be read by an Indian and so forth. But I don't know how you could get anything similar out on the open market.
Best of luck