In BCC Research, search for drone, and you will find a report for Drone Technology and Global Markets, as well as reports that have chapters about drones.
In Marketresearch.com Academic, search for drone. There is a report here titled: Commercial and Military Drones: Technologies, Solutions, Market Outlook, and Forecasts 2016 - 2021, as well as others.
In IBIS World Industry Reports you will find a report for Unmanned Aerial Vehicle (UAV) Manufacturing industry in the US.
In EMIS, search for Technavio and click on Technavio Regional Market Assessment Reports, and then switch to their Global Market Assessment Reports. Search for drone or unmanned to find relevant reports.
In Business Source Complete, search for trade, academic and news articles using keywords such as: drones OR uav OR unmanned aerial vehicles.
Also see resources such as the FAA's Unmanned Aircraft Systems page, AUVSI (Association for Unmanned Vehicle Systems International) and UAVSA.