I'll bet you could make your own powdered butter using melted butter and tapioca maltodextrin (Ab-Zorbit or N-Zorbit). Just mix the butter with the powder until it is absorbed and a very light 'solid' consistency, then rub through a fine sieve over the popcorn whilst you toss it.
I think this would work really well as the stabiliser is quite sweet anyway, which might be good and you could flavour the butter before powdering it.
You could also make peanut butter or nutella popcorn this way.
This also has the advantage that the pop corn would not be getting wet, and the butter would return to butter in your mouth.