luckily i did have one spare black subbass filter.
i used superglue aaround it to its diameter expands and it becomes a tighter fit. if ure careful.enough, i'd recomment everyone to do it to prevent the filter from falling off
+ another neat idea, you can take a needle they use for taking blood to check for sugar.. its called a lancet (?) *i use it for pimple popping*. anyway, the ddelecate needles are thin af and u can use superclue on the needle to cover the hole of the transparent filter to turn it into the black filter and vise versa
and
https://penonaudio.com/ indeed does have them. good find. but 50$? is that a good asking price?