If you're asking for a mod/program that would allow you to have an Uzi instead of a Tec as a terrorist, I'll have to stop you there and point out that this is considered weapon hacking and that you'll be banned on the spot if caught using it. On the other hand, changing the aesthetics of your Tec is okay.
So Nikola, you're saying that if I have an Uzi mod and I'm gonna change it into a Tec9 mod. It's considered as weapon hacking?
Modifying your weapons to look differently for you is allowed, as it is simply a cosmetic change. However, enabling your weapon to function like another weapon is strictly prohibited, as it realistically affects other players in the game.