Help for a total newbie - trying to make a little motor into a large slow fan

I'm game for learning more about small electronics but my current experience is near zero, so I'd really appreciate some help using small words

I need to make a large, slow, lightweight fan with a small motor. In particular, I'm making an Inspector Gadget costume for Dragon*Con in September and I'd love to do the iconic helicopter fedora (e.g. https://thechronicleherald.ca/sites.../B97161203Z.120130322183201000GE12IKOF.11.jpg). I have lightweight corrugated plastic for the fan blades (the kind you see yard signs made from), I have the fedora, and now I'm trying to figure out how to put a motor in between the two.

I'm stuck on what kind of motor I'd need. I'm assuming something relatively slow with higher power, rather than fast but weak? (Since even though the "helicopter blades" will lightweight, they'll be rather long and therefore take more force to get them going . . .) Is there a specific type of hobby motor suited to this, or do I need an adapter or something?

I'm really a total newbie at any hands-on electronics, but this seems like it shouldn't be that hard to do . . .

A small hobby motor with high-ratio reduction gearing, e.g worm gearing, should do. Your local model shop may have something suitable.

You can get small motors with built in gearboxes (or rather, gearboxes with built in motors) - they are often sold as "servos". Just connect a battery and away you go.

I'm wondering if you can get a moulded polystyrene fan from somewhere - it would be even lighter and could be more "showy"

My local hobby store stocks a small inexpensive motor and gearbox that is used in small radio-controlled airplanes and helicopters.
It runs on 2V to 4V.

Or google for "Tamiya" brand motors with plastic gearboxes. They are cheap and common.

If you use a large pulley on the fan shaft and an "O" ring type belt running on any tiny motor's shaft it will turn slow. If you can find an old Walkman type cassette player, you can attach your fan to a slow turning spindle in it.