The ac to dc Atari US 2600 Power supply CO16353 / CA014034 $10.95
Additionally: a Voltage Regulator, 7805 (TO-220) within the console. costs about $0.50 (you are better off with the 7805 1 amp version vs. the original 1/2 amp version 78M05 within the console). This will require soldering to remove/replace. There was an upgrade to 1 amp to prevent units from failing prematurely due to static discharge.
Need parts go to best=electronics on the web
Go to: http://www.best-electronics-ca.com/2600_Tech_Tips.htm#based
Hope this helps.