One of the best sites where you can download maps,patches etc. for swat4 is www.gamespot.com

Demo: www.gamespot.com/pc/action/swat4/downloads.html?mode=demos 

Patches: www.gamespot.com/pc/action/swat4/downloads.html?mode=patches

Maps: www.gamespot.com/pc/action/swat4/downloads.html?mode=maps

Other Files: www.gamespot.com/pc/action/swat4/downloads.html?mode=maps