Are there replacement couplers that work with magnets for Thomas and/or the cars?
HGC
Are you talking about the toy cars with the wooden track?
Because then you should just call the service department, or buy a new one.
The ones that run on HO electric track.
HGC
They are called knuckle couplers, and no.
I checked, nope.
It would be possible, but the couplers will have to be metal. All the couplers' magnetic poles will need to be the same facing the track. Since like charges repel, you will need the same magnetic pole for the track facing up toward the magnetic couplers. However, it is too complicating for manufacturers to make their products compatible with all the other manufacturers.