Pac-Man Fever was a real and dangerous thing. If these "wavers" are any indication, every person in the early '80s gobbled up useless tie-in crap like so many power pellets.
This Pac-Man waver isn't like the window-clinging Garfields or "baby on board" signs I see so much of these days. They were designed to go on the inside or outside of a car window and bob as you drove around town. That's an invitation for theft and vandalism (In my reality, all criminals are drawn to vintage video game junk).
If you're interested in tracking down your own Pac-Man waver, I've found two auctions. One is selling a whole display box of them for $49, while the other is offering a single waver for $9. Considering these wavers came out in 1982 and might have degraded (especially since they're made of cheap plastic), getting the entire box might be the safer option.