Hello @mike1941 I have an APEC Water Systems reverse osmosis system that also has a UV light installed under the kitchen sink. It fills a small tank (about 3 gal) and will regenerate that in a few hours. They also have whole house systems. These RO units are available at retail stores or direct from the company. On my RO system, the filters are easy to change, and not too expensive.
Here is the link to the US company. There is also an overseas company that will come up when you search for APEC Water Systems, but this is the real link to them. They do send out e mail notices when they have replacement filters on sale. https://www.freedrinkingwater.com/