1/2" wheel bolts for spoke wheels

Anybody have a source for these, I can find BWP numbers for the nuts, and cleats but nothing for the bolts. Used on K-5 thru K-7 20" spokes. 5/8" bolts are available, but not interchangeable.

Looks like I am going to have to make my own. I need about 4 or 5 bolts. I ordered the minimum order of nuts, so if someone needs some nuts I'll have a bunch (I hope) left over. I figure if the bolts are NLA, the nuts will be next. I have some cleats but they are still available new. With a spare supply of bolts, nuts and cleats I should be good for sometime.