a) There currently is no way to obtain the Shield of the Hammerhand; not even by paying with real money. The only exception would be if somebody pre-ordered HD, didn't use the code and sold it to you now. Four months after release, the chances for this are slim, to put it mildly.
b) Don't get too excited about this item just now. Update 13 is just around the corner and the current Bullroarer build has a changed functionality of the Shield of the Hammerhand. To be specific, this item does not currently stack with either XP boost pocket items like the Token of the Honburg or with the XP-disabler on Bullroarer. If this makes it to live unchanged, the Shield will no longer provide a semi-permanent way to get +50% XP on crafting and monster kills.
German, female, migrated from CodeMasters in 2011, Premium member, slow-leveller, pure PvEer and opposed to Forced Emotes - wherever I fit into the statistic, it's not in its middle.