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I dont think there is one relevant to the century, the only known image of a "pre imperial" Centurion is the grave stone of an unarmoured Centurion Minucius Lorarius from Padova (Caesars Legio Martia):
Notice he wears his sword on his left and carries a vine stick as a badge of rank, the sword with its lobbed pommel is known from archaeology (and datable) so may be a key to its accuracy?
The strap end wrapped round the belt and hanging down with multiple ends is what predated the imperial "groin" guard...
Most manufactures tend to fill in gaps using imperial kit, but Zvezda has a couple of officers in their Republican Roman infantry which are better then most though the sword of the centurion is on the wrong side and of course theres only the two: