I tried using Sega Parts for a CDX adapter and when I sent a message asking if it was an original CDX they said that all they were selling were Model 2 Genesis adapters as replacements.
the problem with this, as I understand it, not all CDX's like using model 2 power supplies (CD's won't play apparently)
as for OP, yes, you can replace the plug end going into the CDX TRIPLE CHECK that you have the polarity correct!