There are many supplements for liver support and blends are made by major supplement brands like NOW foods. They usually include milk thistle, dandelion, NAC, turmeric, etc.
I usually use WebMD to search for supplements for a specific condition.
If you want to check the efficacy of a specific supplement, I recommend that you check the meta analyses of scientific studies on Examine.com.
There isn't a whole lot of proven supplements to support kidneys, except calcium and sodium bicarbonate (baking soda).