Usually, bike racks aren’t offered on typical rentals. Hertz says that a 4-bike carrier is available for certain vehicles, but you’d have to call them for the details.
If you have a good trunk-mount rack, like a Saris Bones, it’ll fit just about any vehicle, and carry up to three of your bikes. Bonus, that it can also be used on the cars you already have.
If your rental already has roof rails, you could add bike carriers to it, as well. I’ve put cargo carriers on rental SUVs before. Just don’t leave any scratches (electrical tape around the clamps works pretty well)