I don't know how I missed this thread when it came up but I make my own wooden airstones out of basswood. They are 2"X2"X7" with a 7/8" dia. bore.
I screw in a nylon fitting from TSC stores with a 3/8" barb for the air line which is supplied with some of the air from a Pondmaster AP100 linear compressor.
The main skimmer has a foot cube receptor at the top but the other four just have a cereal container for the receptor.
MY SKIMMER PAGE