Hi Dave
This is one that I made for myself. It is quite over engineered as the only spare suitable timber I had lying around was some 3/4 in marine ply. I lined the jaws with 5mm leather to hold the pieces but stained it which I regret a bit. It works really well and is a doddle to make. The only change I would make to the design is to splay the jaws out a bit more by making a slightly obtuse angle to the seperating block on the base.
Pic below and I may have a plan somewhere if you PM me your email addy.
Cheers
Craeg