What kind of options do apartment dwellers have in this space? I've been thinking of DIY-ing something like this (suck in air from the window, heat it resistiv

What kind of options do apartment dwellers have in this space? I've been thinking of DIY-ing something like this (suck in air from the window, heat it resistively in the rare event it's too cold inside, pass it through a HEPA filter, pass it through a humidifier, enjoy), but that is clunky and I'm wondering if products actually exist that I could just buy instead. (I own my apartment, but no HVAC system. Through-the-wall AC, steam radiator heating.)