I'm not aware of any aftermarket barrels for the PT145, much less anything that would accommodate a silencer. And I know Taurus doesn't make one like you're wanting. I guess you could have a gunsmith do it for you, but you'll likely void the warranty.
Did your friend tell you the hoops you have to jump through for a silencer? There is a $200 tax stamp you have to pay to the BATF, forms, and a waiting period. It's not all that easy.