One of the bolts fell out of my head ;-) and I can't find a replacement, either at local bike shops or online. I did find the same size bolt at Ace Hardware with a hex head and am using that temporarily. The size is a M7 x 20, tapered socket head. A 5mm allen fits it.
Anyone know where to find this? Here's a picture from a UK website that sells them http://www.tastynuts.com/acatalog/TISC720.jpg (I don't want to order it from that place b/c it would cost me $26 for 1 bolt!)
