Supplier site id details with API

We have a requirement to get the largest existing supplier site ID for a given supplier and procurement BU, as well as a lookup value that is stored in Saas Lookups. We also need to get all supplier sites under a given supplier where the supplier site id field is empty. Right now, we are getting this data using BIP, is there a better way to get this data without using BIP reports? (For example, with API)