After visiting Mission Chinese in Oakland California, I went away wanting more. It just so happens that this place has its own cookbook available on Amazon, https://amzn.to/2Bp99ei. You need to check this out. It is amazing!
https://www.missionchinesefood.com/sf-menu/
Recipe
1 cup Red Rice Vinegar
1 cup Rice Vinegar or akazu vinegar
1 cup sugar
Half onion sliced
Half green bell pepper sliced.
1 tbsp Sambal Oleak
1 1/2 tsp ketchup
1 tbsp garlic
Cornstarch slurry (optional)