You can skip the bolts all together. I just bought some 304 stainless rod and drilled the endsfor cotter pins. A washer and cotter pin on each end keeps the pin in place. Quick and easy mod.
 
SS Rod

Yep, me too. 3/16" 304 or 316 stainless steel rod. Except I cut some threads on each end for a castle nut plus cross drilled for a cotter pin.