1. Stir together the soy sauce, rice vinegar, water, sugar, garlic, lemon juice, sesame oil and 1 tablespoon each of the green onion and ginger. Stir in the chile sauce to taste. Set aside.
2. Bring water to boil in the bottom of a 2-quart saucepan with a steamer insert set over, but not touching, the water. Arrange the mushrooms in the steamer, top side down. Place the bok choy over them and top with the remaining 1 tablespoon of ginger and green onion. Cover and steam over medium-high heat 5 minutes.
3. Add the pea pods and shrimp. Cover and steam until the shrimp are pink and firm and the pea pods are crisp yet tender, 4 to 5 minutes. Divide between 2 plates and serve with some of the sauce (reserve the rest for another use).