To be honest, in todays world, I don't think Vans Aircraft should sell OR authorize anyone to sell stencils.
While 98% of the uses would be innocent enough, like the banner flags many of us have in our hangars, garages, "person" caves, and the like, there remains a real risk of the copyrighted/trademarked logo being used for less than innocent purposes.
Sad commentary on the US population, but we all know them peoples exist. Right down to having to over-police our very nice classified forum in this web community.