Without counting the vehicles of GTA there’s no real buggy in game, yes trophy truck, dune buggy, but real desert buggy no… or just 1 or 2 so i suggest this one that look good and cool he came with a special livery created by an other person :
The buggy : Buggy Baja - GTA5-Mods.com
The livery : Baja Buggy Monster Energy Livery - GTA5-Mods.com
I hope it’s not an already suggest vehicle, if so, sorry.