I'm a custom stockmaker and recently went on a quest for the bolts myself. Good luck. I thought I could find them locally. After several hours on the internet, I found a wholesale fastner supplier who I talked into selling me his last stock for $14 each (I bought 10). He was almost apologetic at charging me that price. Said if he bought bulk, the price would have been $3 or $4, but he had only bought a box of 100 several years ago. If you're really in a bind, I think Wenig sells them for $25 each. If you want to try your luck, they are a socket head 6 x 1 x 140mm.