Amazon discounts a selection of Berkshire boys' and girls' winter accessories. Plus, take an extra 20% off via coupon code "20PRES15". Even better, Prime members bag free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it starts at around $5.) A couple best bets, with prices after coupon:
Sears offers the Disney Girls' Frozen Snowflake Pendant for $20.99. Opt for in-store pickup to avoid the $5.75 shipping charge. That's $4 below the lowest total price we could find for a shipped pendant. It comes with an 18" chain.