Hello. I've bought a N300 case and I was suprised to see that it doesn't have any dust filter for the gratings on top and sides: the two gratings on the top are around 12 x 12 cm, the one the right is 12 x 23 cm and the one on the left is 13 x 13 cm. For the top ones I bought these even though they may be too thick (since they're supposed to be attached to a fan), I will keep them if the PC doesn't overheat. But where can I find filters that will match the two side gratings? Thanks for the help.