Two tricks, both of which depend on your situation
CAR:
I used to go to my car and take a nap. Kick the seat back, eye cover, maybe ear plugs and put the alarm on vibrate and in my shirt pocket.
Depending on someones situation and their proximity to their vehicle, if they drive.. It could be good.
YOGA MAT:
Everyone likes being hip and yogic. Buy a yoga mat. By tying yoga mats to napping it seems all so, much, more okay.
It's easy to lie on the floor, once you learn to nap on the floor you'll have the most refreshing naps ever.