4GB [2x2GB] DDR2-800 (PC2-6400) RAM Memory Upgrade Kit for The Apple MacBook 13.3" 2.13GHz Core 2 Duo 5,2 MC240LL/A (Genuine A-Tech Brand) at Amazon.com
Used - Very Good: Intel Core 2 Duo E6400 - Core 2 Duo Conroe Dual-Core 2.13 GHz LGA 775 65W Processor - BX80557E6400 Processors - Desktops - Newegg.com