If this is where the square drive rod mates to the round rod on a powergear electric slide, you want to find a grade 8 bolt long enough so that the shoulder of the bolt covers both areas where the shear stress is located. It's ok to use a few washers on the threads if required as long as you have clearance.
Once you find the right bolt, buy a few spares.
Realignment is fairly easy. Get the slide fully extended and use a large crescent wrench on the square tube. You should be able to flex it enough to allow the alignment and get the bolt/nut installed. I've had several break until I learned about the grade 8 bolt with the shoulder long enough to keep the threaded portion away from the shear stress area.
Fred