Yubico[yubico.com] has offer Buy two YubiKey 5 Series keys, get the third YubiKey 5 NFC for FREE.
Offer Terms: Customer must add the YubiKey 5 NFC to cart; the key is not automatically added. Discount is automatic in cart. Redeem at yubico.com only. Standard shipping and handling rates apply. Cannot be combined with other offers or coupons. Not valid for resale. No cash back. No cash value. Offer valid through March 31, 2020.