Take the other bolt out and head to your nearest Ace hardware... they will most likely have it or at least something the same size and thread. Be sure and ask one of the guys there to help you... they can find it in minutes where it might take you much longer.
Being as you are in Dallas, definitely go to Elliots... they will certainly have it...
Don't go to Lowe's or Home Depot... they only pretend to carry odd size shape bolts and nuts...