Free standing enclosures and enclosures that attach to your home can be bought as kits or you can build your own quite easily and inexpensively ($100 to $300). A query to your favorite search engine (enter "cat enclosures") will yield information and photos. You can add extras like height extensions and extra wide shelves for those extra wide felines.
Enclosure kits can be Spartan, however, so add additional shelves, ramps, platforms, cat trees and other equipment to entertain kitty. Large branches or small stripped trees make great natural climbing poles. Just be sure to attach all equipment securely, and be sure the enclosure can support your improvements.