The best strategy for finding statistics is to identify the stakeholders (governments, companies, organizations) and do a thorough search of their publications and Internet pages. Keep in mind that it's possible that the data you're seeking might not be available in the desired format. It could be that no one is currently collecting it, it's not accessible online, and/or it might only be accessible for a fee.
The data sources in this guide can provide a good starting point for your research. Some additional tips for finding data: