Found out that this unnamed LEGO Arc Trooper is actually a named Clone in Season 3 episode 2 (“ARC Troopers”). He is seen for a few seconds and goes by “Hammer”. I
LEGO Star Wars Minifigur - ARC Trooper - Elite Clone Trooper with Rangefinder (2012), € 29,99 (2700 Wiener Neustadt) - willhaben