Here is a solution that I wish I had thought of years ago.
This little bench is 13-1/2" high with a 1" x 3-1/2 x 8" top. You can't really see them in the photo, but the top has a row of nine 1/8" x 5/16" miniature dog holes. The whole thing can be clamped in a vise or to the surface of a larger bench. The third option, shown here, is to sit on the splayed wings that form the base. Two bolts in the top act as screws for the wooden end vise.
Read more about this and more elaborate arrangements in this article on miniature workbenches.