Quick google search bings up the following;

http://www.x2vga.com/

Also, I'm guessing you simply want to switch display between the PC and the xbox right? If so a KVM is not what you want....

A KVM switch will allow you to use both your PC and XBox without having to unplug and switch wires back and forth. You plug the XBox video cable into the KVM on one side. Then you plug your computer's video cable into the KVM, and then plug your mouse and keyboard into it also. Then, the KVM has a place to plug your computer monitor into, and then a USB cable that goes into the computer to relay the keyboard and mouse back to it. You will still have to unplug your K/M to plug into your FRAG, but you wont have to switch any monitor cables...

Most KVM adapters are designed to be used with 2 computers, and in turn, most if not all, use USB to route to the computer. The FRAG is not USB, so it would obviously not work well. If you get a PS2 model, that would work fine.

If you purchased a VGA switch, you could switch from PC to xbox in a wink of an eye. This would be a cheaper alternative, because it wont require a HD pack. You would need a switch which consisted of a VGA cable from the switch to the PC, a VGA cable from PC to Switch, and the standard cable from xbox to the Switch.