can anyone post a pic of the correct screw that should be used on this positive battery cable bracket.

I will look in my assembly manual to see if it lists a part # for the screw,then check with the GM dealer and have them look up the part number to see if it gives a physical description of the screw.

Just a side note, I have never taken a screw out of one of these brackets even on low mileage original cars with original battery cables. The assembly manual shows it, I have just never found one there. I am guessing it would likely be a 5/16" hex head machine bolt.
Rick