These art supply stores in your area should sell drawing materials such as pencils, paper, and erasers (like the 'kneaded' eraser, everybody's favorite in class!):
Santa Cruz:
Lens Art Supply
142 River Street
Santa Cruz, California 95060-2749
(831) 423-1935
Palace Art & Office Supply
1407 Pacific Avenue
Santa Cruz, CA 95060
(831) 427-1550 phone
1501-K 41st Avenue
Capitola, CA 95010
(831) 464-2700 phone