If you want to buy something, buy a huge hard drive. Even the slowest still-sold hard drive you can find is 10x faster than you need. If you get a 4 GB drive, for example, that's many many hours of recordings you can do.
When I made this video:
https://www.youtube.com/watch?v=WURh4w5vjhk I captured over 1000 hours of gameplay at 20000kbps, and for all that, one 4GB hard drive wasn't enough. :)