Given that Retrieve a Company is available via API it should be available in SDK
https://developer.infusionsoft.com/docs/rest/#tag/Company/operation/getCompanyUsingGET

https://github.com/infusionsoft/infusionsoft-php/blob/975ea80207f5d17e19b9dee12544997d4c3ed9c8/src/Infusionsoft/Api/Rest/CompanyService.php#L9C32-L9C42