Yes, there are. Some cultivars are mentioned on my Tree-page . I want to buy a female Ginkgo. Female Ginkgos are for sale. Many garden centers sell the Ginkgo biloba.
Special cultivars are for sale at a nursery.
The Ginkgo can often be found in the conifer catalogue. Best condition is one that will dry the leaves quickly but not overheat them. Never dry leaves in the sun. When the leaves are dried, put them in a paper bag inside a plastic bag, and store them in a cool, dark place - in a tinted glass jar is best. For dosage read the site of the American Botanical Council and the related links on my Links-page .