I made this out of nothing more than ductboard, A/C metallic tape, A/C sealer, flex tubing and a bathroom exhaust fan.
Basically it's just an inverted box that is about 6 inches larger than the dryer. Sits about 4 inches above the dryer on 2 cross boards where I fastened about 3 blocks on each cross board to create small tunnel areas for air to flow up and out from all the sides to the flex tube from the top.
Lightweight and cost about $75 and it works nicely