Actually California black worms and tubifex are 2 different worms. Google California Black worms.
If you can't find them where you are, Canadian Aquatics out of Vancouver has them
http://www.canadianaquatics.com/equipment/equipment.htm (near the bottom of the page).
You can get some and if you have some room you can culture them.
This book will help you.
Culturing Live Foods by Mike Hellweg
ISBN: 9780793806553
Hardcover, 240 pp.
Cheers,
Vic