I was unable to find Ficus tremula for sale in the US so I am resorting to growing them from seed. It will take many years for these now two month old seedlings to mature into a reasonable bonsai. Growing from seed is for the young and those with lots of patience.
Ficus tremula bonsai grown by Hennie Nel of South Africa
Ficus tremula at two months of age grown from seed
For more information on growing figs from seed see:
http://www.bonsaihunk.us/ficusforum/FicusTechniques/FigTechnique33.html

The definitive reference work on Ficus
for bonsai. The book is a softcover, 8 by 10 inch volume, with 144 color pages, containing detailed information for the beginner as well as the advanced hobbyist.