[mazuhl]

You should start making your own screencasts and sell them alongside the others. Your brand is already established, you'll have seen enough screencasts to know what works and you can identify gaps in the market. If you put an open poll on there you can get feedback from people visiting the site about what they want to buy, but isn't there. And you can share that with other screencasts producers. If nobody else steps up, you can make and sell the most popular suggestions.

You don't even have to make the screencasts, you can pay others and you just sell them.