Unfortunately there are no such small NFC Tags yet, but we are working hard to be able to provide them to you.
In the meantime, you can check out our smallest Tags:
ICODE® SLIX 6mm round for metal
NFC Glass Tags ICODE SLIX2 4x22mm
NFC Stickers NTAG213 16x16mm
NFC Stickers NTAG213 10.5x19mm
Photo by MARCIN CZERNIAWSKI on Unsplash