I've had to do this as well in the past. You have to get your freelancer rep low enough, and just right. make sure the last place you docked was Barrier Gate Station. Every so often some freelancer NPC's will roll though, and yes zoners. either or, shoot em as much as you can, watch your rep. Get down to about 0 or just above, then sundive and check for the bribes. it can sometimes take a while :/
I tried doing Zoner missions, but never noticed any increase on freelancer rep from doing them, but i could be wrong!