How to get sports memorobilia certified w/ a certificate of authenticity?

When I was around 10-11 years old(1990-91ish), my parents took me to a Philadelphia Phillies spring training practice in Florida. It was just practice, so most of the players had plenty of free time. I managed to land a bunch of autographs from famous players.

So here I am 15+ years later, with a baseball signed by Lenny Dykstra, John Kruk, Darren Dalton, and Mike Schmidt(this was by luck, he was down there visiting practice, not still playing), and about 15+ other players whose name I can’t even read.

Anyways… i have this baseball, I know these are authentic autographs. But who do I send it to, to be certified as real? And how much does this generally cost?

PSA is the most reputable company. They can be a bit pricey but they are the number one company out there for authentication.