Canadian student interested in intern/summer job in the US

What are the avenues for a Canadian student to get a summer job or an intern job in the US?
Say if there is a US company that is willing to offer a summer job to a Canadian student, what king of visa is the most appropriate?
There is J-1 but it seems it needs to be done via one of "designated sponsors", that have their "host companies". But what to do in case of a US company that is willing to hire a Canadian student to a summer job, but they aren't associated with any "designated sponsor"