Bi-metal strip is not the sort of thing you find in the stores in town - I think you will have to go to a specialist repairer or "borrow" a similar strip from a broken appliance.
If you're in the US this place may be able to help you...
Household Appliance Sales and Service Inc.
7034 N. Milwaukee Ave.
Niles, IL 60714
Toll Free (800) 786-2326 • Local (847) 647-8250 • Fax (847) 647-2214
Peccavi, March 2009