Where can get good Exemestane

Where can get good Exemestane? A lot of people don't know this stuff, and here's the introduction to it:

According to the chemical name of ischemittan, 1, 4-diene-3, 17 - diked-6 - methylene or 6-methyl-androstan-1, 4-diene-3, 17-dione, white or white crystalline powder; Odourless. Dissolved in trichloromethane, dissolved in ethyl acetate, acetone, methanol or ethanol, almost insoluble in water. Clinically applicable to postmenopausal patients with advanced breast cancer after the treatment of tamoxifen.