You didn't state whether you are looking for LPs or CDs or downloads, but if you want vinyl, Mobile Fidelity has reissued a lot of Frank's albums. I have all of them and most of them are stunning.
My favorites:
Swingin' Sessions
The Concert Sinatra
Nice 'N' Easy
My favorites:
Swingin' Sessions
The Concert Sinatra
Nice 'N' Easy