I had a couple requests from European folks to post the commercial seed sources I found for those tuberous cactus genera. Here goes... http://cactusstore.com/category_60/… http://www.cactusplaza.com/seeds/cactus-seeds/ http://www.mesagarden.com/c2016.html And this place seems to have a lot of species... but not sure if it has tuberous cacti types. http://stores.ebay.com/BOTANICAL-ARCHIVE/… Happy Gardening! Dennis in Cincinnati