Where can I get an UNSECURED line of credit with my terrible credit?

I am looking to acquire a line of credit to be used as overdraft protection in the event I need it. Unfortunatly, I made some very poor decisions several years ago, and now I can't get approved for anything. I can't finance steam off a hot dog. Where can I get an unsecured line of credit for this? Nothing wildly extravagent, just maybe 1 thousand smackeroos max. None of those prepaid cards are what I want, if I had that money, why would I pay a service to hold onto it? My credit score is about 560 - 580.