Wow, thanks guys. I just thought I could wander down to the local store and buy one as they are so useful. It's amazing how hard it is to locate some things here that I would consider a no brainer for a country with sketchy water supplies.
I remember ceramic filters in the DR years ago. People with decent tap water supply preferred units that were attached to the faucet.
As your own link indicates, these filters "improve" water quality but do not remove or kill all harmful impurities (such as virus and some bacteria). They also need frequent cleaning and eventually repair or replacement.
Worse, you still need to find the water to put in (not trivial, depending on where you are).
Now, here the common drink water "solution" for most urban and many rural areas is the "botellon" (big purified water containers). It's a relatively inexpensive "all in one" solution. You get the water and the purification process included for a modest price, and may even get it delivered home. Seems to work well for most.
That means that filters are manufactured or imported in relatively small quantities, which implies relatively high price (versus mass market solutions).
You are welcome to try something else, but be aware that you'd be "swimming upstream" so t speak.