When will Tera shop include more weapon skins?

  • I was going through TERA Shop and can't even find many, many skins that were bought/sold on tera broker but not even on the shop so I was wondering how people get them in the first place. When new weapon skins come out is there an event and then you can never buy it again? I really want the Velik's Vigor of the Sun or Uriel's Sacred Staff. :/