Shoot some Xenos or Hogosha. Otherwise unless you want to try your luck with the Liberty Rogues, it's very unlikely that any Junker is going to want to talk to you, so those that would offer you the bribe normally on non-Junker bases will not. You need a non-Junker for the rep hack. A Liberty Rogue or Bundschuh could help you, in theory.
Bartender of Niverton Rogue Base in Pennsylvania offers Junker Bribe, you can try your luck there. (You can normally get double bribe there as well, but I dont think it applies to your case, cause a Junker gives the second bribe, who wont talk to you cause you are red, so no bribe!)