On further observation the git repository of the book [0] seems to be quite active. Maybe this book might be finished after all.
22 karma · joined January 4, 2021
Here are some of the popular brands that you can get over here:
https://www.eurekaforbes.com/water-purifiers/by-category/aqu...
These claim to use RO, UV etc. for purifying the water. I am kind of surprised that the Amazon USA listings for water purifiers return several fad-ish "gadget" things first, instead of the above.