At the hobby store.
I've got a toilet tissue core covered with red construction paper on which
I've printed "DANGER!" and "EXPLOSIVES".
When the little tricksters come to the door, I'll say "Just a sec," reach
behind the door where lies my faux dynamite and a candle.
When I swing back, with the sputtering-fuse big-banger, I'll say: "Okay,
which of you little darlings wants a trick? Heh-heh-heh!"
Last year I had some really thick glasses and made out like I couldn't see
their bags as I dropped the candy.
Little kids are so much fun to mess with!