If you have the pictured Gammill bracket, the bolts are:
A: Alloy Steel Button-Head Socket Cap Screw 10-32 x 3/4 (McMaster # 91255A269)
B: Stainless Steel Button-Head Socket Cap Screw 10-32 x 7/8” (McMaster # 92949A270)
You should be able to find them at a hardware store that carries specialty bolts, but they can also be ordered from www.mcmaster.com using the part numbers listed.
For any other bracket, please contact us and send a picture of the bracket.