In another old thread a member had a picture of his now-retired setup with one of those clear plastic spheres that were popular years ago as covers for commercial lighting in parking lots and along sidewalks etc. He said it worked well for years, but of course was neither optical quality nor easily available unless you were there when they were pulling an old install or wanted to pony up the bucks for a new one.
I'm not even sure what the official name is, but they sort of look like a space suit helmet, completely spherical and in his picture, was clear.
I have non-weatherproof AXIS camera, with pan-tilt-optical zoom which, while not HD, is darned good, and I'd like to mount it out of doors rather than looking through a dirty window with limited views. The 9" dome from AliExpress will be a smidgen too small, and I don't see larger ones, but I'm looking.
Someone mentioned looking for an aquarium or terrarium at a pet store or a place like Micheals but none here are big enough to carry much more than some polished stones and a few goldfish, so again no luck there.
Finally, I found a cake stand and cover made out of glass, something I remember my grandmother had 60 years ago, but the owner didn't want to part with it. The optical quality was poor, but it would have been a start, and unfortunately all the ones I see in the kitchen stores now are plastic. Funny how they don't make them out of high-quality research-telescope quartz glass any more. I just can't understand it.