The width is dictated by your printer settings, under Page Setup.  I assume you've tried switching to landscape?  You can change the paper size, to buy yourself some more room.  If you select the No Printer option, then you don't have to worry about the printer settings restricting you in any way.  You still have to pick an existing paper type, though, as far as I know.  I'm not aware of any infinite canvas option.

Keep in mind, though, that this means that you may not be able to print the report, depending on what you select.  This may or may not be an issue for you.

Yup, that's pretty much what I said.  Just in more detail.

Oddly enough, the one time I did need to do something like this was at a company where we did have a plotter on the network.