The easiest way to replace the DLC port is to find a vehicle exactly like yours (or even a close relative) and cut one from it. Then splice the "new" DLC port into your wiring, if you can find the point at which it was cut from the car. This would be an OBDI port you'd be looking for. If you do go this route, take as much wiring as you can get a hold of beyond the port itself. It's a lot easier to cut the wires back than it is to add to them.
I looked for a replacement plug and was unable to find one. I would bet you will not find a new replacement for it anywhere.
I would bet that any 3-pin Honda DLC from an OBD car (95 and older) would probably do the trick. Also, it should be located up under the passenger side in the kick panel area. I'm sure your mechanic knows this, though.