I guess your looking for a factory type of original style bolt(s) but a regular hardware store purchased bolt will work just as fine.
I have put a couple of KH brake systems back into service using regular style bolts without any issues what so ever.
One, two, three, or all four of them.
At one time, a guy up in Canada reproduced those bolts, or had some company do it for him, but that's been quite awhile now...