Where do I find the Weight Variants of an Airbus aircraft?
The weight variants for each model are listed in the aircraft's type certificate which describes the type's compliance with airworthiness regulations. You can look up the type certificates from regulators such as EASA and FAA.

As an example you can look at the document for the A330. Each of the minor models (-300, -200, and -200 freighter) has its own section, and the weights are listed in the "Technical Characteristics and Operational Limitations" subsection. Below is the table showing some of the A330-200 weight variants. The maximum takeoff (MTOW), landing (MLW), and zero-fuel (MZFW) weights are defined for each variant.