Looks to me like you're stuck with AGP graphics.
I hope I'm wrong.
The best you're going to do (for a reasonable price) with AGP is a ATI 3650 for $40.
Just an FYI, you're getting performance similar to a Nvidia GT 520 or slightly better than Intel Graphics 3000 so you're not going to be doing much in the realm of demanding games.
Main: i5-3570K, ASRock Z77 Pro4-M, MSI RX480 8G, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod