In the US I've only ever seen sawfish in big mixed predator exhibits. The "standard" mix typically includes Sandtiger and Sandbar Sharks, Southern Stingray, Goliath Grouper, some sort of jack, some sort of sea turtle, and perhaps 5-10 other species. Sawfish (usually Green) are one of the other species you get in these tanks. Off the top of my head I can recall seeing them at Baltimore, Shedd, Sealife Minnesota, and SeaWorld Orlando but I'm sure I've seen them elsewhere too.