Basically the current status is like this:
VME bus: NI does not sell any hardware for this anymore and aside from some special manufacturers nobody else either
MXI-2: NI has issued a last buy for end of this year for the VXI-MXI-2 interface which is the last MXI-2 card they still actively sell.
PCI: Most PCI has been obsoleted too by NI or will be obsoleted soon. And PCs with PCI slots are hard to come by nowadays
So yes you have a serious problem if one of the hardware components decides to die. Your best bet will be companies like Apex Waves, ArtisanTG, or ValueTronic who sell refurbished hardware and have various NI hardware in their program. It's very questionable that you can find a suitable solution from another vendor as VME really is a legacy product since a long time.