Maybe they have some of the cutout fans from the COVID season somewhere in the basement they could haul out for it? Or, to your point, hire seat-fillers a la Oscars?
The real problem is the swell home plate club they tie to these seats. When the game gets boring, or the weather too hot or too cold, or they just have someone in the seat who's there for business and doesn't give a rip about the game or about baseball in general, they're going to the club to schmooze. This is a problem all teams create for themselves by chasing the short term dollar.