There's no such thing but you can make one, I use a rockband drum kit pedal on my computer, i had the encoder board of an x-arcade lying around from when i replaced it with an i-pac for my arcade machine. It uses an 1/8th inch plug but works basically the same as a sustain pedal. I got one of those project enclosure plastic boxes from Radioshack and threw the encoder board as well as the led indicator light, program switch, and an extra button to trigger the program mode. The x-arcade is programmable, but you have to have the program mode selection switch available as the default mode 1 is not programmable, and you need a button or switch of some kind to change it from the default mode 1 to the program you specify every time it is powered up, and the light is there like it is on the original x-arcade to help with the actual programming, done by connecting a ps/2 keyboard to that ps/2 female connector hanging out of the enclosure.

I imagine the cheapest, simplest keyboard encoder available, or possibly one of them game controller encoders will meet your needs for one input