You will have to remove the stem and get a photo and the measurements.
Sometimes it's easier when the stem is out, to take it to a plumbing parts house to order the parts.
This is why plumbers love simplicity.
Delta, Moen and Price Pfister have just a few parts.
Kohler has more parts, that can be a problem,
The boutique faucets, they can get their body parts from anywhere.
And Pegasus, they don't have replacement parts or web sites.
Pegasus is one and done. If it wears out, you just replace the entire faucet.