I got 60 Gasparini 9mm balsa filters (3 packs x 20) from Amazon for $15.99 and 120 6mm balsa filters (3 packs x 40) for $16.99. They took awhile to get here; I think they ultimately came from China. Smoking Pipes has 9mm and 6mm charcoal filters by Savinelli. I don't always use filters, as I find they restrict the draw too much, but it's nice to have then on hand if I choose to use them. I believe Amazon still has the Gasparini filters in stock.
I've also used the spiral aluminum 9mm Tsuge Kulu filters a couple of times. I'm not sure if the spiral lengthens the smoke path for a cooler smoke, or acts as a condenser; I need to experiment with them more (draw is not restricted, which is nice).
I've also used the spiral aluminum 9mm Tsuge Kulu filters a couple of times. I'm not sure if the spiral lengthens the smoke path for a cooler smoke, or acts as a condenser; I need to experiment with them more (draw is not restricted, which is nice).