I got a set on ebay for $60 I believe. They work great.

there is an easier / free way if you are small time (i.e. start w/an oz or so at a time) and all you need is a coffee filter.

here's what I do...

you need a blender. nice size cocktail one works great. something that could crush ice. Take an oz of bud or great trim (no fan leaves, stems, etc) cleaned, ground, put ice in the blender. less than 1/4 full. pour (spread) your herb on top of the ice. let it sit for a minute to cool. Have a jug of ice water on the ready. add enough water to cover the ice, and crank the blender up.

If it gets stuck (smoothie effect) turn off the blender, add some water, stir, repeat. the shit should get ground up. A few minutes of blending the herb smoothie.

I pour this all in a tall thin glass container and wait for the ice to finish melting and the goodness to fall to the bottom. get out the crap that floated to the top with a slotted spoon, getting as much as I can (goodness sinks, veg rises). Then, I carefully siphon out the water above the settled material, except for 1/2 inch or so above the sediment. The remainder, I run through a mesh strainer (was told a hop bag works great for this step) then I put through a coffee filter. I use the coffee machine to hold it, and catch the runoff in a coffee pot. be meticulous and you end up with some nice shit. Good bud (Jacks Cleaner) yielded 8g/Z.

Take the stuff in the filter, scrape it out onto a plate or something to dry, then press and enjoy

good luck!