Rice protein powder that is not already blended with pea and other plant proteins is a little harder to find.
Hemp protein powder can be harder to find at a more reasonable price. Unfortunately this is due to the restrictive legislation on hemp crops in many countries.
Casein protein powder is fairly easy to buy from most health food, supplement stores and chemists, as well as online.
Plant protein powders have been steadily increasing in popularity and are now far more widely available in health food and supplement stores.