Have you seen those inflatable bouncy thingies that kids play in at carnivals? They have high output fans that keep them inflated. Now, those may be too big, but there are also smaller inflatable structures with smaller fans. You could use one of those.
I did a google for inflatables (man, they have inflatable technology in architecture and space exploration!), and didn't find a supplier of just the fans, but I'll bet that if you are diligent you can find one.
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