Reshala appears with a 5% chance on Customs. He can be found in dorms or at the new gas station. 

Reshala is accompanied by 4 well-equipped Zavodskoy guards. Reshala himself has no armor. You need to kill him and take from his dead body. This pistol must be found in raid, meaning you can't just buy it at the flea market for this quest.

You may be out of luck because when you kill Reshala, the golden TT may not appear, as he might have a different pistol on him.

Do not forget that you cannot put the pistol in the secured container. It is necessary to leave the location alive, so have 5000 rubles with you just in case of possible extraction through the “Dorms V-Ex” , if you killed the Reshala in dorms.