OK, 8/32 is the size of the small Allen hd bolt that holds the bumper on.
The wght. bolt itself is 3/8x16, industry std.
Schon has a custom cut hd on their wght. bolt.
Otherwise, a std flat-head stove bolt will work if you can under-cut the shoulder. But then you'd have to drill & tap for the bumper bolt (8/32).
As fate would have it, the wght. bolts for my cues are exactly like Schon's.
But I'm kinda puzzled when you say a 'heavy 1 inch bolt'.
A 1 inch bolt will weigh what it weighs. There is no light, med. or heavy 1 inch. Please explain.