Fi Nano Partner's cannot share Fi Nano microchips with other vet/rescue/breeders as there is no way to transfer the microchips ownership from one Fi Nano Partner to another.
Once a box of Nano microchips have been purchased, they are automatically registered with the contact information of the vet/rescue/breeder who purchased the chips. This contact information will be used as an additional point of contact if the pet were to get lost and the pet's owner is unresponsive.
If you have already shared microchips with another vet/rescue/breeder, you (the the original Fi Nano Partner) will have to get the pet's information and register the chip under your account. See: I am a Vet/Rescue/Breeder, How Do I Register A Fi Nano Microchip For a New Owner?