hey man,
im not sure how they run things there in europe but i was low on $$$ so i went to youtube.com and watched a Do it yourself video on how to make a carbon filter.
the entire project for the filter costed me less then $15 u.s.d. which is like 10 euro lol.
i used a hepa filter replacement for the carbon paper. made a frame from a thin mailable metal like chicken wire
check it out! they are cheap.
happy gardening,
TeXas