Bought a couple of these today- Colgate wisp
http://www.colgatewisp.com.au/wisp/HomePage
They are designed as single use toothbrush- thought it would be great for overnight or bring along a bit of baking soda for use on multi-day... they are tiny and hardly weigh a thing (give or take a gram- lol). 9cm long and very slim.
Cheers
Lizzy