Extending PS/2 would be relatively easy, just connect a microcontroller to the KB/mouse to interpret their data, then use another microcontroller on the PC end to recreate it, with a more suitable long-cable communication method in between the two microcontrollers (RS485?)
However, the amount of time and effort to build something like that would probably not be worth it unless you're already familiar with microcontrollers, PS/2 interfacing, and whatever other communication method you use. Since it's a project for where you work, you should probably consider your hourly wage, and think of how much it will really end up costing if it takes you 10 or more hours to complete - suddenly the price of the commercial solutions may not seem so high - plus they'd be more reliable than a homemade device.
I also agree with Nigel and Papabravo, this sounds like a bad idea. Why can't you just manage the servers remotely, over the network? Telnet, SSH, remote desktop, VNC, or something like that...