You just need to look at low-profile cards. There are plenty available at Newegg: http://www.newegg.com/Store/SubCategory.aspx?SubCategor... <-- go here.
Click on Power Search.
Third section down is called Form Factor. Check both "Low-Profile" and "Low-Profile Ready"
Next section down is Low Profile Bracket Included. Check Yes.
The next section down is Interface. Check PCI Express 2.0 x16 and PCI Express x16.
Click search and see what TheEgg has available.
What we would recommend depends on intended usage, budget, and possibly your power supply.