They are probably concerned about the job you left after just a few months and of the circumstances of that event. If they insist on the references I can't see a way to get around it. After all, past job performance is probably the best indicator of future performance, and refusing to give a better reference will likely cost you the job as it makes it clear that you are trying to hide something. Unless you have decent references from more senior people, which you should have used in the first place, you might have to just bite the bullet and contact your previous employer to find out what they will say. Note that you might be pleasantly surprised, as unless you were a terrible employee and burned all your bridges there, most bosses don't go out of their way to screw you over on references. It happens, though.