Helmets

I have a tricycle, and Duchess the chihuahua rides in the front basket. Neither of us wear helmets, riding 6mph on flat pavement there is little chance that the trike will tip over. However, when I ride my bicycles I do wear a helmet and Duchess stays home. There are actual dog helmets sold on Ebay but I have never seen a review. Chihuahuas are pretty tough and hard headed, but I don't want her to be hurt in an accident. Those of you who take your dog along on bicycle rides, how do you protect them?