fish filleting clamp

does anyone know where to get a large clamp to attach to a filleting board - like the ones on the fancy american filleting/chopping boards?

Heres a link to a website with some.
http://www.nextag.com/fish-fillet-board/compare-html
Heres the link to the rapala one on their website so maybe a tackle shop that does that brand would be able to get you one of em. http://www.rapalaworld.com/knife.php?s=c2l2dT1rbml2ZXMmaWQ9MTlIaDVDWFZ0