Can't get this thing out of my head! None out there, and if there were, probably an arm and a leg plus extras to buy . . . .
Was bored yesterday, so decided to try to create an extremely primitive and very simple device with at least some level of adjustability.
Having discarded the idea of a load of sliding pins through each jaw (which I really like, but can't do owing to the hassle of clamping the thing up using hydraulics (if only!), some sort of cam action or even a powerful electro-magnet), I just attacked my cheapest Chinese 4" machine vice, drilled and tapped holes for c/sunk screws, and slung it together.
It does actually work, within the limits of the shallow jaw depth and the fiddle of adjusting the screws, and will certainly hold quite a few odd-shaped items for drilling and tapping. Swivelly and/or curvy bits of eg brass on the operating ends of the screws would be nice too, might do something on that later. (Different screws could be knocked up for particular jobs - but I just used what was lying around.)
Anyway, a pic to amuse - and suggestions for 'better' (within the limits of a home workshop!) would be very welcome.