Hit Sally Beauty. They sell to the public, and have up to 40 volume CLEAR developer readily available to the public. It's about $4-5 for 32 oz. From 10 volume(3%) to 40volume(12%) in sizes starting at 2 oz up to gallon sized jugs. They also sell a cream version of each 9f the developer strengths, but you don't want that. It's got extra conditioners and thickeners in it to facilitate blending with bleach powders or tube gel hair colorants. The things we women will subject ourselves to for the sake of beauty, huh? 😜