Lichens - These can be found on landscape stones at most landscape supply houses. Horsetails - Call around to aquatic plant nurseries. Equisetum hymenale is very widely available. I got my specimens from a road cut near a local creek. Dawn Redwood is widely available from local nurseries.
Cycads are also available at most local nurseries.
Ferns can be purchased locally, or by mail-order from many different places. Local plants are best, as you can then visualize how you'll do your planting before you purchase. Gingko biloba . Gingko is thought to have been preserved up to the modern day due to the habit of Buddhist monasteries to plant them in their temples. It is thought that there are no truly wild plants in existence.