Magan/Makan was roughly modern-day Oman, and the image above is clearly derived from an Angus MacBride depiction of a 3rd/4th century AD "Omani marine" (I do not know what MacBride used as source material), so quite a bit later than the end of the Achaemenid Empire. That said, if you want a similar looking figure I think the 100 Years War helmet (+ some Green Stuff?) and Gallic shield kitbash idea is a great suggestion, as I've seen no existing miniatures that quite fit that image.