Used Lenovo ThinkPad T61, T61p, X61 or X61s. They’re all quite durable, have matte screens, and (when equipped with Core 2 Duo processors) will easily outperform the Atom in the stock Classmate. And black matches everything.
The T61 series is in your size range, and can be had for $250 or less (I can send you a couple links if interested). The X61 series laptops aren’t that big, but can come with a high-resolution screen with a 4:3 aspect ratio (useful for displaying the driver station readout below the camera output).
Make sure the battery is good (or spend a little and buy a new one). You can run TPFanControl to force the fan to keep it very cool, if that’s what you want. (Fan noise won’t be a problem in an FRC driver station…)
Use it before the end of the build season, so that you know everything works. (If you can’t do this, it might be best to get a new laptop instead to minimize possible failures.)