You could try this one , but the problem is I haven't seen a benchmark done on x4 video cards. If you want you can get a pci-e adaptor to make a x4 slot into ax16 slot and then you could put in any card you want. I have even seen someone take a soldering iron and make a grove in the back of the x4 slot so the end is open and a x16 card will fit . I don't have a x4 slot on my MB so I don't know if there is a solid end or an open end on a x4 slot , you should be able to tell by looking at yours.
StarTech PCI Express X4 to X16 Slot Extension Adapter for 1U Servers Model PEX4TO16Rhttp://www.newegg.com/Product/Product.aspx?Item=N82E16815158288&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Add-On+Cards-_-STARTECH-_-15158288
Maybe you could use this.
Thanks for the assistance. It helped. My situation was that I had purchased a CQ5810 computer which only had a PCI Express X4 graphic card slot. As suggested in this blog, I examined the slot and noticed it was open in the back I tried an X16 slot GE Force 9800 Graphics card and it did fit with a hangover in the back and it worked. Windows 7 Experience Index now gives both Graphics and Gaming Graphics a 6.8 score. So, I think my problem is solved. It leaves me with the impression that the pins on an X16 slot are not implemented or necessary beyond what is necessary for the X4 slot. That is my "novice" opinion and may not be correct, but what works works. Thanks, Earl Carson.