http://www.newegg.com/Store/SubCategory.aspx?SubCategory=574&name=CPU-Fans-Heatsinks
You'll have a huge choice of aftermarket heatsinks and fans to choose from to replace your stock heatsink and fan. And if you spend about $25, you'll almost certainly get something that is better and quieter than what you had before anyway.
As Aerlinthian said, you'll need to be sure to get one that is compatible with your motherboard. For Intel, socket 775, 1155, and 1156 are pretty common sockets and you can find some heatsinks that will support all 3.
If you want to keep the price down, this CM Hyper TX3 is pretty nice for just $25. It supports socket 775, 1155, and 1156 (1155 and 1156 have the same hole spacing).
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103064