I've made my own too, but it was a cable for Palm DSLR software. Now I'd like to move to DSLR shutter software wich runs on PC but can't find 4n26/4n33 optocoupler specified
here in any local store. There was a online one which has them in stock but I waited three weeks while they process my order and canceled it at the end. I probably can try to re-use the one I made for Palm but I guess it requres some modification to be done to wires connection.