Amazon.com: AMD Radeon R9 280X 3GB HDMI PCI Express Video Graphics Card for Apple Mac Pro, outperforms ATI Sapphire Radeon HD 2600, 4870, 5770, 7950, 9000, 9800 Gigabyte : Electronics
Gigabyte R9 280x 3GB GPU for mac pro/efi,boot screen,metal,4K | eBay
Refurbished: GIGABYTE Radeon R9 280 Video Card GV-R928WF3OC-3GD - Newegg.com