Well, you've already ordered the fan now (which is the best option),
..but you could've also put two 12V fans in series on the 24V rail. Or just place one fan on the 5V rail (which will mean it'll spin (a lot) slower, but maybe sufficient.)
But like I said, your solution is a lot cleaner (and fans aren't that expensive yeah.)

Where did you buy the Nylon from? Want to do some testing with it too, and since NL isn't that far from UK shipping should be the same here.

But tonight I want to do a quick and simple test with a sphere without a flat bottom.. basically almost no surface for first layer. Let's see if that adheres to the Buildtak?