iMac Intel 27" EMC 2429 Radeon HD 6770M Graphics Card - iFixit Store
iMac 27" Video Card Upgrade | MacRumors Forums
Amazon.com: Genuine Graphics Video Card for Apple iMac Late 2009 A1311 Core 2 Duo 3.06 21.5 Inch Desktop PC MB950LL/A MB950, AMD ATI Radeon HD 4670 GDDR3 256MB, MXM VGA Board GPU