Kim Kardashian is saddled up for summer. The reality star soaked up the sun on her Hawaiian vacation in a black Gucci string bikini finished with the house’s gold horsebit hardware. The price tag on the tiny two-piece? A cool $1,300. In case the suit was too subtle on its own, Kardashian, 45, added a diamond double-strand belly chain for her day by the ocean. Indoors, she layered on a sheer black bolero and black leggings for a monochrome look. By the Skims founder’s standards, the body jewelry is relatively modest: In 2023, she turned a Messika necklace set with a 17-carat pear-shaped diamond into a belly chain for Michael Rubin’s…