Very Nice. Are you using an air brush gun of some type? I have a COPIC system for which I am having trouble finding air cannisters.
God Bless America
Yes, I used Copic markers with the Copic Air Brushing System. The little cans of air, D60N, are hard to find and very expensive. The last ones I purchased were online from JoAnn stores. I don't always make poppers, but when I do, these expensive little bottles of compressed air are convenient. What is really great is not messing with paint, you just pop the Copic marker in there and paint.
I use the same system. They once made a D90N can, but can't find that anymore. As you mentioned, the cans are hard to find in stock and on the expensive side. I also noticed that they have changed the shape of the pen and holder (gun) somewhat. Fortunately I have plenty of pens for my original gun. I think I bought my set about 5 years ago.
God Bless America