Not sure if many designers still aim to market any set products, but over the last year or so we've been promoting Pressure Seal documents, there's a lot of money not just in the printing of them but also the design. They have to be set and designed to exact specifications and can often involve many changes before final approval but if you can get a few clients that use them and you can get a good name in the production of them it's a nice market to be in.
I've uploaded a few that I've done recently for people to view...
Taylors Colour Printing - Pressure Seal Documents UK