Most publicly traded companies provide their same stores sales via their Investor Relations websites. To find these sites, try searching [company name] investor relations using a search engine like Google. Search for same-store sales or comparable store sales.
Search Statista: Try a keyword search for same-store sales or comparable store sales.
Also be sure to check SEC Filings for US publicly traded companies and SEDARfor Canadian publicly traded companies. Try doing a keyword search for same-store sales or comparable store sales.
Mergent Investext - Do a Keyword search for same-store sales or comparable store sales.