HORI announced the release of the dedicated New Nintendo 3DS LL Grip release with the logo of the Monster Hunter Double Cross.
The new grip will be available on the same day as the game, March 18, 2017 and the price will be 2678 Yen (with tax).

It will be available only for the New Nintendo 3DS LL. You can already pre-order it from the Amazon Japan: http://www.amazon.co.jp/exec/obidos/ASIN/B01MXRGR2C/