While not as common as soymilk powder, rice milk powder can be found in some stores, or fairly easily online. Brands such as Better Than Milk are fairly well distributed. Since it is free of dairy, lactose, soy, and gluten, this may be an excellent option for many food allergies and intolerances. Use equal parts rice milk powder in recipes calling for milk powder.
Ingredients, processes and products are subject to change by the manufacturer at any time. All products should be considered at risk for milk cross-contamination. Always contact the manufacturer prior to consumption.