I did a test render to see if I could get the correct dimensions to the toy that uses parabolic mirrors to create a hologram. The result is attached. I used Add/Mesh/Extra Objects/Math Function/Z Math Surface with the equation:
1 - ( x2 + y2 ) for a parabolic surface. X and Y size was set to 2. Afterwards I Scaled it to 5 times size. Then Scale to 0.23 on the Z.
Copied using Shift-D, Rotate-y-180 and in edit cut the small hole in the top. Made the material mirror, and added a small item to project in the hologram.
The other picture shows the camera view (the torus shaped hologram is not visible).