Marimo Balls can be purchased at just about any Petsmart.
For other types of moss, if you don't mind the drive, try New Wave in Orange. They have Fissidens, XMas moss, subwassertang, and riccia.
I don't think Tong's or 405 stock moss that often. Neptune's Reef I think carries Java Moss and Willow Moss. Its been a long time since I've been there though, but its got one of the better plant selections that's sorta close to Long Beach.
The for sale forum on SCAPE might be another option.