Look at the reviews. I think it was the second poster that said he needed to drill holes to be able to do what you want............ unless you install the fans on the out side of the case and screw them from the inside. Then you can attach the filters the way you want.
You should only put filters on fans blowing into the case as if there is any dust trying to get out let it!
I am assuming that you are looking for round fans to cover each of your 12 cm side fans. I have two Thermaltake VA8003 Armor cases each with a 25 cm side fan blowing inwards to the motherboard and bought a couple of magnetic round filters from a South African company and am very happy with them. He made them special order for me with a black fabric rather than the white fabric he normally uses. The magnetic strip is about 1cm wide and a couple of mm thick and is black and shiny so when it is on it looks like original equipment as it just does not show. Pull it off to clean blow if light dust and use water if really dirty.
I got mine because my Mother In Law had her machine fry a powersupply and video card with dust buildup and although hers was not an expensive machine mine is a more pricey gaming rig so I dont want to take any chances.
The filters are very fine but do not seem to have a whole lot of air restriction to them so as long as you watch them regularly for dust buildup and clean them regularly they should be good. I am looking to put a few more on the frot of the case too as I dont know how long the existing filter foam will last and I as you cant wash them I am concerned that over time they will plug.
He was pretty decent to deal with and the filters came to me in Canada in a couple of weeks which surprised me a bit as Canada Customs usually are a bit slower than that to process things. The price was reasonable too.