You can make up your own solution, 

0.01% avidin D in PBS, 15 - 20 min, rinse

0.005% biotin in PBS for 15 - 20 min, rinse

Proceed with primary antibody, etc.

Purchase stock chemicals from Sigma.

be sure to do this block AFTER a normal serum block since serum can
contain endogenous biotin 

If you do antigen retrieval, this also brings back the endog biotin

Gayle Callis