The following images were shot using a piece of white lexan. It takes a little time to bend this using heat. This stuff is pretty unbreakable and once bent, holds that shape.
The lexan provides a great reflection and the shadow is pretty much eliminated. If you want the shadow instead of the reflection, just lay a piece of paper on the surface under your object. It is large enough (if you are shooting small things) that it will cover your framed area.