“Keep your head in the game and your Mac off your lap”

Laptop Shelf (see below)  15.5” Width x 9.5” Length x 7.25” Height

Closest available shelf

You can find it here  (affiliate link) ︎
= 10.4 x 15.6 x 8 inches
taller (.75”) and slightly longer (1”) front to back
It requires that you break off the side rails to easily fit it inside your briefcase.