I wanted to add a HEPA filter to my XC1. Looked for some suggestions around MakerWorld and at the usual sites but I didn't find anything fast, simple, no brainer, and I was inclined to use the HEPA filters that I have available easily, at least in Brazil.

Found the Electrolux filter kit, model 147A (images attached).

From this filter, I designed a very simple frame that would fit the aforementioned filter in one end and was easy to fix in the X1C's chamber ventilation exit at the back of it.

The filter is attached to the frame in a tight fit and then the frame is attached to the back panel of the X1C with double-sided tape. Well, I have designed first the frame with 2 magnets inserts (15x5mm size magnets) but then I got worried that just the magnets would not provide a sealed connection to the ventilation exit. So the double-sided tape, in this regard, is a more suitable choice, in my opinion.