The two big ones on the market are Travalo and Flo.
I have a few Travalo and I like them. They work really well.
The Flo is pretty much the same but you have more options for filling them.
They are pretty cheap. The Travalo is $10 or so.
I have several of the Flo atomizers. I don't just use them for traveling, but also for frags which either don't come with atomizers or would be better if they hadn't. I often place samples in the Flo for a better application as well. I haven't had good luck with the pour-from-bottle method shown in the videos even with a funnel - spill too much. Instead, I found that transfering the frag from the bottle to the atomizer with a pipette works much better... http://www.youtube.com/watch?v=ocsrkuJeXpM