This is a very hard one to track down. The only one I know of that is identical electrical wise from sega is the official cdx power supply. There are others sega adapters that will have the jvc running but like the poster said there are a lower amperage. so running the jvc with the lower amperage isn't good (so says people in the electrical know).
You have to be vigilant looking and looking. There are extensive articles on it online. I carry the cdx/jvc power supply number in my wallet so if I come across it in the wild I will pick it up because it is so easy to get confused due to the different model sega adapters.