The Rainbow Clover is not sold as a standalone item. Instead, it is bundled with specific outfits in the Fortnite Item Shop :

Part of the Green Clover Set , which includes other festive items like the Sgt. Green Clover skin and the Pot of Gold harvesting tool.

While it often returns around St. Patrick's Day, it has appeared over 30 times in the Item Shop since its release. In-Game Appearance

The is an Epic rarity Back Bling in Fortnite, primarily recognized by its vibrant green three-leaf clover design with rainbow accents. How to Obtain

It was first introduced during Chapter 1, Season 8 (March 2019).