I found these pre-filters on Amazon. Cheap and you can cut to fit with scissors. I just drop one on the top and let the suction hold it down. I don’t know how much it will help with dirty cuts, but it might extend the filter life a bit.
https://www.amazon.com/gp/product/B079M61PQB/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&th=1