AKASA make some pretty decent, cheap HSF solutions but it all depends on the amount of space around your CPU socket.
You'll see that a lot of fans don't list socket 7 compatibility on the back, but some will - even some of the more extravangent models (using an Athlon cooler on a K6-III+ system myself). Don't count on this as being the norm though, as some Duron/Athlon heatsinks are just too big. They usually have the dimensions on the side of the box.
On my other K6-III system I have an AKASA AK710 and I paid something in the order of £2.50 for it. Very fast and very nice on the ears, which is another thing to bear in mind..it may be worth spending a little extra on something that is going to be quiet. The 710 measures 56 x 60mm, so measure the space you have around your CPU to see what you can fit just to make sure (some socket 7 boards are really badly designed and the space can be extra small).
Also, what core voltage are you using? You could hit 500MHz with some thermal paste and decent fan, even higher.
Hope this helps.
. AMD CPU Data: http://www.tomshardware.com/20.../amd...ult/page23.html
. Belarc Advisor: http://www.belarc.com/free_download.html
. GPU Comparison for Laptops: <a href="http://www.notebookche