Where can I find this 셔츠 in GTA V online?

I saw a player character in GTA Online on PS4 wearing this black 셔츠 with short purple sleeves. I wanted to find that 셔츠 but I couldn't find it in any of the clothing stores. I wasn't able to ask him cause I didn't really think of it at the time. I actually don't even know if it was a t-shirt. Might've been a whole outfit thing 또는 something but either way, I have not been able to find it. Is it something 당신 achieve from doing something 또는 was it part of a pre-order thing 또는 what?