Product review (5 stars): Adjustable Dryer Periscope from Amazon
This unit works well and was easy to install if you put some furniture mover pads under the feet so you can slide the dryer after connecting one end of the Periscope to the dryer outlet and slip the other end in to the vent pipe, tighten the clamp and do it all without needing another person.  You can cut it to size or not as it fits both ways.