i would try printing the filter part as a flat surface (without retractions) directly on the printer bed (only 3 layers maybe) and bend it later to become a tube ( like a “C”) i am not sure about petg, i did this bending with pla. hot water comes in handy and maybe a glas bottle. also prepare something to tighten where the ends of the C connect, a border without the small filter holes but some larger holes for something like cable ties or even a printed part for connecting the C edges.