Try the Knightsbridge Dual Band chin strap. It's the only one designed to actually work. The Knightsbridge lifts from below the jaw and has two bands (one elastic, one non-elastic), so it can be adjusted to actually work and be comfortable.
The cheap neoprene ones you find on Amazon wrap around the tip of the chin and push your jaw directly into your jaw joint, which is the least effective and most uncomfortable angle possible. (Technically speaking, the design is poor because the force provides almost zero "torque." You want the force 90 degrees from what the neoprene ones provide.) I.e., the cheap neoprene ones aren't actually designed to work.
I tried mouth tape, but that gave me a very claustrophobic feeling. I also tried a bunch of chin straps. But don't bother with the cheap neoprene ones they sell on Amazon. They wrap around the tip of the chin and push your jaw directly into the joint. Very uncomfortable. Get the Knightbridge Dual Band chin strap. It lifts from under the jaw and the two bands (one elastic and one non-elastic) make it very easily adjustable to be comfortable. Now my mouth leak rate is very low.
