Check out https://www.pccasegear.com/
I'd choose from a MSI GeForce GTX 960 OC 2GB https://www.pccasegear.com/products/32085/msi-geforce-gtx-960-oc-2gb
Or a MSI Radeon R7 370 Gaming 4GB https://www.pccasegear.com/products/32278/msi-radeon-r7-370-gaming-4gb
Personally i'd choose the R7 370 with the 4GB's of vram but check craigslist or any local buy/swap/sell sites to see if there's anything that interest you.
Good Luck.