Starting on March 28th, fans who buy 3,000 yen or more worth of Zoids Wild products at participating stores will receive one of three random customize weapons.

 During April (and most of March) (3/28 ~ 4/25), users will receive 1 random weapon from the Command Attack Unit Silver Titanium Ver. They can receive the Bone Blade, Grinder Cutter, or Panzer Faust. During March (starting 4/25), they can receive 1 random weapon from the same weapons unit, instead having a chance to win the Arc Knife, Auto Saw, or Square Shield. If users purchase 3,000 yen or more worth of items during both of the campaign periods, they'll receive one additional (random) item: The Mega Lance, Wing Cutter, or Attachment Frame.

 So where can you get these? There are no stores (to my knowledge) that offer guarantees. However, amiami appears to be the most likely to send out purchase campaign benefits. While HLJ occasionally gives out campaign benefits, it is usually a part of their own campaigns, and not a part of the original purchase campaign. Otherwise, keep an eye out on Yahoo Japan, etc.!