A suitable substitute would be any cream containing active skin-lightening ingredients like kojic acid, arbutin, glycolic acid, and vitamin C. These components work together to target hyperpigmentation, similar to your current formulation. Since you apply this in a 1:1 ratio with azelaic acid cream (your other cream), it is important to choose a substitute that is gentle and fragrance-free to minimize the risk of skin irritation. Please consult your dermatologist to select a specific generic formulation that safely fits your skin type and maintains the efficacy of your current routine.