You can use a tie down, either the kind the is over their nose and tied to the girth or the kind that hooks to the halter and to the girth.

You can also use a running martingale. It gives the horse freedom of him head until you pull back on the reins, then it aids in having the horse bowe his neck instead of toss in the air.

Neither are severe and works extremely well! I used them while re-training my OTTBs!