Here's an option: Hirobel Frame Clamp | Jenson USA I've seen other brands so shop around. Never used one myself so can't give a review.
Option #2: Tell your friend to buy his own special stand.
Option #3 Hang it on a storage rack. 1 example- Two Bike Gravity Stand – Delta Cycle (designbydelta.com)
Option #4 Tell friend to get a metal bike.