The whole idea is to get you to buy a manual first, and look up the part number.
Then order the part.
All of these units are made like this. It's on purpose.
And so what you want is to find somebody with the service manual, or download the shop manual, etc, or a tascam parts place (this one is pretty good...) http://teactascamparts.com/
but find that manual because it will help you now and in the future for sure...