Making a blender built for 120V work on 220V
The best part to exchange is the blender. Sell the 120v one. Buy a 240v one.

The 240v motor will probably cost 90% or more of a new blender anyway, once delivery, and the non-mass-market cost of supplying spares, have been taken into account. Then you have to fit it, with the risk of damaging motor or blender. And then you have a junk 120v motor cluttering the place.