Reddit mentions of Paragon Butter Flavored Seasoning Salt

Best I could find http://www.amazon.com/Paragon-Butter-Flavored-Seasoning-Salt/dp/B002YLGAIO

That one just looks like a typical air popper. They're around $15-$30. I got this one(#2 Best Seller on Amazon) from Fred Meyer, and have owned it for about a year. It's great, no complaints, and the little cup on top for butter is even the perfect size to measure out how much popcorn you're supposed to put in it. My dad has an older model by the same company, and after around 7 years, it still works almost as good as when he got it.

As for seasoning it, ignore what /u/JustGreg said about using oil to pop if he likes the buttery flavoring. Oil popped popcorn is awesome(I have one of these too), and coconut oil that's been artificially colored and flavored for popcorn is what you should get if you want movie theater style popcorn, but if he likes the flavor of butter, just put butter on it. Take 1/4 to 1/2 a stick of butter, and either microwave it(AFTER you pop the popcorn, unless you have a 25 amp circuit in your kitchen!), or leave it on the the cup on top of the popper while it pops, and drizzle it on the popcorn after it pops. As for salts, I like Flavacol, which is what a lot of theaters use, Paragon Butter Flavored Seasoning Salt, or Jolly Time Buttery Popcorn Seasoning. Or if you're as lazy as I am, you can just pour some of all three into one of these.

Just remember with the air poppers, the only thing that ever goes into the area where it pops is popcorn, never put butter, oil, or seasonings in while it pops!