You don't need it.
Filter through a cloth first, maybe twice. Then use coffee filters. You might have to change filters during filtration because they do clog up fairly quickly, but it's still cheaper to use more coffee filters than building a vacuum filter, and in my experience it's not really THAT bad.
vacuum filter is fancy, probably kind of cool to use, but definitely not necessary for a successful extraction, nor for good yields.
cheers&love
Enoon