If you can't locate one a spacer/sleeve on a more standard bolt may get you by.
The washers are removable and there is a metal one and a rubber like one. 7/16-14 thread. Under head length is 1-1/4". Shoulder is 5/8" long and just under 5/8" diam. Looks like a seat belt bolt, but coarse thread. A similar bolt from another year may work. Thanks!
I have one with a 9/16 depth shoulder, if you think you can use it PM me