Vantec Iceberq Copper, or Iceberq4 (measure the distance between mounting holes on the Radeon 8500 - the Iceberq Copper has more closely spaced holes).. I have one of each - an Iceberq on my motherboard northbridge, and an Iceberq4 on my Radeon 9800 Pro.
Whatever you do, clean the GPU and bottom of your HSF with rubbing alcohol, and use high quality heatsink compound, such as Arctic Silver III.
Another worthwhile alternative is the Zalman HP-80. It's more expensive ($25), and it's a hunk'o'aluminum, and it'll take you a half hour to put together, but it will cool your Radeon very well without the use of a fan at all. Guaranteed to outlast your video card 🙂