Internal parts for the CW-80 are not available from Lionel, as
it's not considered a "user repairable" item.
That said, the fan is just one of those 12VDC sealed bearing
mini-fans used in many computers. The trick is finding a triangle
tipped screw driver to open the case with! ;^)
When they show up at my LHW, I plan to replace my CW-80 with one
of the new Atlas-O 80 watt transformers that don't need a fan.
Plus they allow "common ground" wiring of track and accessories
like the older Lionel transformers did.