Good luck finding one.
I have a cheap, easy replacement option if any one is interested. A while back when the Turbo-list was still thriving, me and another member did some testing and found that the output specs listed on the adapter for the TG-CD unit are not accurate. Why this is so is unknown to me, but the good news is that Radio Shack makes a cheap AC adapter that outputs the correct voltage and amperage needed by the TG-CD deck (at least, they used to).
IF anyone is interested I will find my old data and post it up. Surely a much cheaper and easier choice than trying to hunt down an original NEC adapter.