Can air filters of the wrong size be used to make a DIY air purifier?
That the machine is cheap and the replacement filters are nowhere to be found… Chef’s kiss to predatory capitalism.
For reals: In a capitalist country, you can accidentally pull a predatory capitalism without intending to. It’s how you respond when someone points it out that makes you as a person.

I’m sure you can, if you rig it to something like a fan to pull the air through and seal the points of contact between the edges of the filter and the air intake.