There isn’t a substitute but you can use the following ideas to create a nice-tasting dish (despite not being authentic). a) Use homemade spicy black bean sauce, or commercial ones like Laoganma black bean chilli sauce (老干妈风味豆豉). In this case, you can omit fermented black beans in the recipe. b) Mix an Asian fermented bean paste (e.g. Chinese yellow bean sauce, Japanese miso, Korean doenjang) with Chinese chilli oil or a hot sauce of your choice. N.B. You may need to adjust the quantity based on the saltiness of individual condiments.