Commercial driving insurance is provided by most major companies that employ drivers. If you are self-employed or your employer doesn't cover your insurance (common for taxi drivers) then you'll need to find a policy that works for you. Plan pricing varies depending on the type of commercial work you do, the miles you will drive, the type of miles (city versus highway) and the type of vehicle you drive.
Different companies treat commercial vehicles differently. Some have one policy for all commercial vehicles while others have more specified coverage depending on your vehicle. For instance, one plan has three options for pick-up trucks: liability insurance, physical damage coverage and uninsured/underinsured motorist.