i’m a laser hobbyist, probably i can help you a bit:-)
ideally i want to project large sphere in the middle of gallery space,
but if it turns out to expensive/difficult than maybe a set of single
I dont exactly understand what you want, probably you could describe it more precisely! You want a real sphere (like a ball) in the "air" or a circle on the floor?
the circle on the floor will be available for 5 EUR, the 3D sphere for about 19000 EUR ;-)
Depends also on what colours you want! And: lasers are quite dangerous to eyes and even skin! I’m not shure if you can see my email adress (its my first post here) but if you want write me a mail with more specifications! I’m shure I could help you to find the right point to start!