Heat grill to high heat. In a large bowl, toss the first 5 ingredients (fish through lime juice). On large skewers, thread fish and onion.
Place skewers on grill and cook for 5 minutes on each side, until fish is cooked through. In the lettuce leaves, layer the fish, onion, and avocado. Drizzle coconut aminos over the lettuce wraps and serve.