Brakes probably aren't a great option. What are you trying to accomplish? If you're concerned about fast taxing or long landing runouts, the best way to approach that is with pieces fuel tubing placed on the axles. Compress them against the hub of the wheel with a washer and the wheel collar. That'll introduce a little more friction.

I've seen a brake put on the nosegear of a .40 size model, and the most charitable way to describe it is ineffective. It was a drum-brake produced by Dubro, if I remember right.