Ah yes.
Just found this pistol model on Sketchfab, thought it looks cool, so I ported it into Source.

UPDATE 2/8/2022 :
Just now realized it's based on F.E.A.R 3's Strader Mk. VII pistol, oh well.
https://fear.fandom.com/wiki/Strader_Mk._VII

Gmod version:
https://steamcommunity.com/sharedfiles/filedetails/?id=2738819806

Includes:
sketchfab\bcfbox\skf_bcfbox_future_hand_gun.mdl

Credits :
Eliott Lilly - Original concept of F.E.A.R 3's Strader Mk. VII pistol.
Mark Bai (@bcfbox) - Original creator of the model.
NeoLin - Porting to Source.