That sure does stink. You may want to speak to the manager about it.
A saw like this with a saw guide is quite easy to use to cut your panels down to size. Since you can set the cutting depth to be just below the thickness of a single sheet of hardboard, you can cut the panel on the floor or on a folding table in the garage, holding it up off the table/ floor with cheap 1x2 or 2x2 furring strips. No need for saw horses or a table saw. Lay the panel on several 1x2 strips that are running parallel to the cut and make sure the blade doesn't touch your support surface.
You will need to transport the full sized panels which is going to require a truck. Maybe a friend can help if you don't own one.