For such questions always take a look at https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills which lists polyfills for almost every new feature.
Which contains a list for LocalStorage as well https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills#web-storage-localstorage-and-sessionstorage
In particular, this one seems active: https://github.com/marcuswestin/store.js