a chambon. far nicer, far better, not very trendy any more unfortunately. very simple for the horse to understand (pressure only comes on when head is raised, so he has a large comfort zone), and, unlike the pessoa, it won't sock him in the chops with every stride of his hindlegs...
Rideaway and Derby House both stock copies of the Pessoa, and I can't recommend them enough - or at least the 'actual' Pessoa one anyway!
It doesn't need to 'sock it in the teeth every stride' if fitted as loose as is safe to begin with, and then you can tighten it as the horse gets used to it. Unlike most training aids it not only helps teach the horse to work in a good frame and into a contact, but at the same time it encourages the horse to step under more with the hind legs and take the weight behind. Most other 'tools' only work on creating something in front, and we all know that it has to start from behind!
It's worked wonders for my ex-racehorse in getting him to accept the contact, come off his shoulders, and carry himself from behind!