My mistake, I thought you said you didn't want to take it off.
Do this. Take one of the hex nuts off and drive down to your local ACE hardware. They always have bolt thread testers that you can get close with (or at least eliminate some possibilities). Failing that, root around in the bolt drawers to see which bolt fits the hex nut the best.
Do this. Take one of the hex nuts off and drive down to your local ACE hardware. They always have bolt thread testers that you can get close with (or at least eliminate some possibilities). Failing that, root around in the bolt drawers to see which bolt fits the hex nut the best.