I have a LEGO city with all the modular LEGO in my bedroom. But the dust is killing me at nights. How can I protect them? Where can I get those display domes?
Where I'm from it's called Plexiglas. Other tradenames are Crylux, Acrylite, Lucite or Perspex... Anyway, you can get sheets of it cut to size in D.I.Y-shops or hardware stores to build your own domes. If you are less handy, you can find lots of shops offering standard or custom solutions. If I google "plexiglas", I find dozens of solutions near where I live. I know of one person who had a custom pyramid shaped Plexiglas dome made for the 10181 set (Eiffel tower)
I know it is a bit simplistic, but you might try just using a light sheet. If it is a light, tight fabric, it probably will go on and off pretty easily.
If you have lots of delicate parts on your buildings, you could get some small stilts of some sort to hold the sheet up over those areas. That will give you the circus tent look, I imagine.