I sponsored my first wife 3 years ago for a Partner visa that was granted, but she left me almost as soon as the visa was granted. I’ve now met a new partner and want to sponsor her as well and lodge another partner visa.

You need to wait 5 years to sponsor a new partner. However the five years is measured from the grant date of the first visa to the grant date of the second visa.

As Partner visas are taking up to 20 months to process currently, you could technically consider lodging a new Partner Visa  application soon.