For $200 you can get a capable fisheye for Nikon Canon (and perhaps other mounts). I got mine via ebay from a seller named rus_camera, delivery took less than a week.
Before buying I read through many confusing articles that questioned the optical quality, etc. One common “defect” is that the lens is delivered without the rear-end filters. The standard Zenitar comes with 4 filters made out of 2mm glas (1 UV, green, red, yellow-greenish). The lens is adjusted for these 2mm glass being in the optical path - if missing the lens will front-focus.