If you have a higher-resolution image, you could get a smoother result, if the product is going to be large. You could generate such an image using a vector graphics program, if you don't have it already. Avoid saving out as a JPEG - use PNG instead.
Hollowed out versions might be cheaper, if what you're paying the designer is less than you save in material.
It would be helpful to give the dimensions you're looking for, and the material. And anything else about it might also make a difference.
If the item only has to look good from the sides and front, you might not need a back to it at all. Then you could still do it yourself through the 2D-to-3D creator - you'd need to use the greyscale option and a bit of tinkering.
If there
is more to it, take up one of the designers who has PM'd you, if you haven't already.
(I could certainly do it, but it's enough messing around that I'd charge.)