Squash blossoms are very tender and you will likely not find them for sale online–they would be very difficult to ship in a timely manner. You would have better luck checking at a local farmers’ market. (You will likely need to wait until spring and summer); ask any of the vendors who sell squash if they can bring you squash blossoms. In the cold time of the year, check at a local produce market–if they have squash for sale, it is likely greenhouse grown. The grower may be able to bring blossoms to the market for you.