Suggestions for temporary high-bandwidth hosting

I don't know if this is the right forum for this, so if not, mods please feel free to move it.

I work for a smallish company that hosts its own Web site on its own servers, and normally we have plenty of bandwidth to spare for day-to-day operations. However, a few times a year, we have a large (50MB or so) update file that upwards of 30,000 people need to download at once. Needless to say, this maxes out our bandwidth and then some.

Do you know of anyone reputable that offers high-bandwidth hosting on a temporary basis? I know there are companies like Akamai that could technically do that kind of thing, but most of the ones I've come across are big and expensive and want to lock you in for a 12-month contract or more. I'm just looking for a place where you can put a file for a week and then turn it off. Kind of like YouSendIt on steroids. Anything like that exist?