Digi-key sells the components, but there is some assembly required.Part number EE-SX1061
http://rocky.digikey.com/scripts/Pro...39&M=EE-SX1061. They're $1.95 each.
You'd need a resistor to limit the current through the emitter side. The peak output is at 20mA, so maybe 330 ohms.
I haven't used it, but I think you connect the collector to the signal input on the input pin and the emitter to ground. It should pull the input pin to ground when the slot is open.
Pin C - RC signal input
Pin E - RC ground
Pin K - Connect to pin E via 330 ohm resistor
Pin A - RC +5V