As you do your research, think broadly and creatively about where your target fits. Some industries are too new or too odd to fit into an established category. It also doesn't hurt to look at more than one industry.
Many databases allow you to use codes to search for an industry. Two codes that are assigned to all US businesses are NAICS and its precursor SIC.
- NAICS: North American Industry Classification System
- SIC: Standard Industrial Classification
If you have trouble finding the right code, you can always look for a similar/competing company in a database such as Reference USA and find the codes there.