Looking for distilled water

We have a friend coming to visit who uses a CPAP machine. She will be in need of distilled water and we are aware that it is the automotive sections of Supermaxi, Coral and Kiwi. We know there are other places that sell it in larger quantities but can’t recall their locations. To the CPAP users in Cuenca what is your source for distilled water, other than those mentioned above?

Many thanks for your responses,

Jerry Ackerman