There were a few posts in the past of people looking to reduce the Nicotine in the shisha so they can smoke the more nicotine rich Nakhla and others. Most sites that sell them always seem to be sold out. I just noticed that Caravan Trading on ebay has them. They are 5.95 for two cartridges good for approximately 15 smokes per.
Just figured some might be interested... Oh yea, free shipping.