MILAN, Oct 27 (Reuters) - Amazon (AMZN.O), through its Climate Pledge Fund, has bought a minority stake in Italy"s CMC Machinery, a company with technology that makes custom-sized boxes that eliminate the need for single-use plastic packaging, the machines maker said on Wednesday. CMC, which is controlled by private equity firm KKR and counts Amazon and Walmart among its customers, said it would use the funds to enhance its search for sustainable solutions and to grow globally. The Climate Pledge Fund is a corporate venture capital fund, with an initial $2 billion in funding, that invests in companies working to develop sustainable technologies. Amazon said on Wednesday the Climate Pledge Fund had also invested in U.S. electric vehicle charging technology group Resilient Power and in U.S. ultra-low carbon electro fuels company Infinium.