Putting the new release as a CD-R* is a given, I would also add an annotation saying that it's an on-demand CD-R from amazon, and probably a disambiguation too.
Too much information is always better than not enough.
That, + the different cover art, should make the release quite identifiable.
*since you're adding releases that you don't have in hand, be aware that you'll always end up making mistakes.
We're making a lot of assumptions (although informed ones) about these releases. An edit note making this clear is really helpful to future editors, for instance - "not in hand, information from amazon, please edit if you have a better source". You might also have to leave some things blank, for instance the release date in this case (unless you can find out when Amazon started offering this service for this specific release)
Ideally we would have a release in hand when editing/ adding, and we want to err on the side of caution if we don't