The early versions of the CDX2 used the Philips VAM1250. These were short-lived and new ones are long gone, so because of this some years back Naim re-engineered the CDX2 to use the VAM1202. At the same time they also offered a re-engineered VAM1202 based update solution for anyone with a VAM1250 machine who needed a new mech fitted.
From what I gather from @NeilS, Naim can no longer offer the VAM1202 update for VAM1250 equipped CDX2s, however, if yours is a later VAM1202 unit, or an earlier one that has already had the VAM1202 update fitted then you should be OK for the time being, although @NeilS will no doubt know the most up to date info here.
If the mech fails in a CDX2 with a VAM1250 then you would need to replace with a VAM1250. Apart from some rather dubious mechs available on certain auction sites, the VAM1250 is long gone and extremely hard to find. You could, of course, scavenge an old working mech from another suitable old player (mech lists can be found online), but that’s outside of what Naim can offer, and being one of the higher-end Philips Mechs means that there’s no nice plentiful and cheap player to source from. There are though a number of “kitchen table” techs that might be able to help here, but again, that’s a discussion that’s rather outside the AUP of this forum.
The CDX2 was a great player but it’s days are, sadly, over. I moved from a CDX2 to an HDX and, while the presentation was subtly different, I never looked back. The HDX uses generally available 5.25" optical drives and 3.5" HDDs. They can be replaced by NAIM, albeit a little on the expensive side. It can also operate as a stand alone CD player as desired.