A few years ago I stumbled across a toy military vehicle that was sized for the 12" GI-Joe type action figures and bore a strong resemblance to a Mk 2/3 Ferret. Unfortunately, I neglected to pick it up, and the store no longer had it when I returned a couple of weeks later. I have looked for it ever since, but have never seen it again.

Has anyone encountered such a beastie? I would really like to find one for a diorama that I am considering building.

I think that you will find that the veh you are looking for is an Action Man accessory. My Bro had one - years ago. I should look on Ebay if I were you.