For a Duron you can get almost any cooler. I built a system for my Pastor with the same processor and I used the retail heat sink and fan.
Are you planning on doing any overclocking... You can but with a Duron it isn't that spectaculor. You should then use something with a little more heat dissipation.
What are you doing with it?
Got a LAN Party that you want people to know about?
Let me know about it.