The Crossroads of the Aether
Excellent work, old chap. Are you planning to rig it so that smoke will come out of those pipes?
Like the hat I would check out your local hobby shop that sells model train stuff. I think they have some stuff for model railroad steam engines.
It looks like all the model railroad smoke varieties require a heating element of some kind, which I'm rather hesitant to put inside a hat that rest upon my thinking bits. The dry ice idea would seem eminently plausible, with several options at that.
The simple option is plug up the bottoms of the pipes, add a little water and drop some dry ice in and viola, smoke. It would be adding a bit more weight to the already heavy pipes however. A more complicated version, but one that would deliver more smoke for a longer period of time, would be to hide a reservoir of water under the hat with 2 feeds connecting to the base of the pipes. Filled with more water and more dry ice it would probably look better but be significantly heavier that option 1 (though it would be balanced weight on top, so probably not uncomfortable).
I'm a bit preoccupied with some other projects at the moment and I need to locate a dry ice vendor in the area, but I'll certainly update when this hat starts smoking! Cheers!