How do you repair a tennis bracelet?

My prom was Saturday night. My boyfriend and date ordered a corsage that had a keepsake bracelet instead of the regular corsage band. Today I put it on and I noticed that it was a little streched out. Upon further inspection, I realized that the little strands that make it elastic had snapped and I'm very upset. Would a jeweler be able to fix this? If so, how much would it cost?