Hey Yoko,
Welcome to the forum.
If it's an older Dolby Labs unit and has an oval shaped hole and three round male blades, I usually just replace the outlet with a regular IEC receiver.
The hardest part is hogging out the hole ( I use a Dremel and files). To remove the old receiver, there are two screws on the bottom of the unit that hole the red "protective" shield and once that's off, you'll see the back of the old plug. Just be sure and mark the poles since they're the same as a modern IEC.
You may be able to buy one of those cords but I don't know what they're called. If you can figure that out, someone like Newark Electronics might have one but if your just guessing, number of possible blade patterns is overwhelming (at least to me!)
