The large acrylic dome came from a company that sells these as skylights for buildings and RVs. While they can be purchased as large as 96" in diameter, it is recommended that you measure all hallways and doorways before ordering. 

Our dome measured 54" in diameter, and 27" from top to bottom, 1.4" thickness and came with a 1.5" flange around the edge. Shipping for the dome equaled the cost of the dome itself. As shipped, it had a split foam rubber tube around the flange to protect it. We had been warned about the possibility of cracking the dome by applying too much pressure on the edge mounts. As a precaution against that, and a protection against people hitting their heads on the edge, we left the foam protector on the dome, and loosely tightened the eyebolts that we mounted through carefully drilled holes. The dome was mounted with one wire attached to the ceiling (on the side facing the operator) and two wires connected to the wall behind it. Another installation might require a custom metal stand.

One major difference between projecting on a flat screen and in a hemisphere is cross-bounce of light. On a flat screen, the most reflective surface is generally desirable for brightest image. In a dome, any bright element can reflect around other sides of the projection surface and wash out other images. For that reason, a darker, gray surface is preferable. We obtained a paint sample chip from the manufacturer of our full-size dome and made an effort to match it with a flat enamel. It is still a constant concern to keep program material at relatively low brightness, and compensate with higher color saturation to make the image "pop". But the mini-dome serves as a useful testbed for program material that will be shown later in a larger dome with a brighter projector.