What you're looking for is called a "retaining clip", though I'm seeing them more often called a "cable clip". These aren't usually considered "replaceable" parts, as they're so fragile. However, I have seen various ones on eBay. The dv7 is common enough, you should be able to find one (I struck out). I warn you, however, that you run a pretty big chance of breaking the replacement as well while attempting installation. It's probably worth it to get the system running again, I just wanted to make sure you understand the risk.
Good luck and make sure you let us know how it turns out!