Halo generating hat

In the old old pictures you can always tell who's been really really good, by the ring of light floating above their heads. Well, since the technology has been lost, and I feel the need to at least appear to have been good, I decided a halo generator needs to be developed.

This idea has passed through several design phases - the Magnetically Contained Toroidal Plasma halo; the neon tube halo; the Moebius Strip paper halo (has a good side, and that's all) and even the somewhat undersized Magnetically Levitated Handcuff halo.

The one I finally decided on, however, is the Stable Vortex Smoke halo. Three metallic bands form a double layer truncated cone; a small battery operated fan inside the cone generates the air motion which results in a stable vortex, about eight inches across, hovering about five inches above the head. A small smoke generator feeds two tubes attached to the surface of the divider cone; these allow a continuous trickle of smoke to rise up into the vortex.

Now I just need help finding something that produces bright yellow smoke, without the smell of Ultimate Evil...