I have no idea what the cost, efficacy, or availability of this product is. https://hydrocell.fi/en/air-cleaners-carbon-dioxide-filters-and-dac-appliances/uniqfresh-air-cleaners/

The only maintenance required is changing of the activated-carbon filter every six months, and replacement of the HEPA filter every five years. In normal use, the carbon dioxide filter cassette has a lifetime of at least 15 years.