There are hundreds of different brands and formulations of progesterone cream. It is considered a "nutraceutical" and is not controlled or regulated by the FDA. You can purchase progesterone creams through the internet or drugstores.
Most of these formulations say they are made from wild yams or soybeans, which contain natural progesterone. Generally these creams are considered safe, however no studies have been done regarding their effectiveness for treating hot flashes or other symptoms of menopause. Progesterone is a female hormone, as is estrogen, and both decline naturally with aging.