http://www.thompson-morgan.com/flowers/flower-plants/annual-plants/cosmos-chocamocha/p95697TM

Thompson and Morgan site...

oops sorry missed half of my comment off last post.. this site says.....

"seed Collecting:
N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed "

http://davesgarden.com/guides/pf/go/29/

so plants are on T&M site, but there are lots of others around cheaper....