Click on any of these links if you really want to try and get an air filter. There are a bunch of options out there all you need to do is look and educate yourself and you can just come here on the forum and ask some questions, there are a lot of people in the same situation who cannot vent outside who have found ways around it. If you search the forum you can also find people selling their units/ air filters as well so you could always make a deal with one of them.
-3rd party low cost air filter
-third party air filter
-This is a google search for “Portable laser filter”
This is from earlier this year as well.
Hope this was helpful in some way and you can get to use your 
as it is a pretty awesome thing.