http://www.learningaboutdogs.com/acatalog/Specialised_Clicker_Training.htmlHave you thought about going to a trainer, either 1:1 or a class where you can be taught techniques that you can use at home to prevent pulling.
Unfortunately there is not a single piece of equipment in the world that will STOP pulling only gadgets that will minimise the pull.
These gadgets would include choke chains, head halters and harnesses. They operate in different ways and you must choose one that suits you and your dog and causes the least pain.
It is worth remember that dogs can only pull if they have something to pull against, hence why it is worth training a dog to walk where you want it to be without a lead at all! :D
The Walk With Me book written by Kay Laurence and available from the above link is only £4 and is very useful; she even runs workshops on walking on the lead.
HTH