For the Marquee template this is the naming convention that works currently:
$("#desktopNav > .main-nav > .nav-wrapper > ul.cf > li:nth-last-child(1) a").replaceWith($(".search-block"));
$("#desktopNav > .main-nav > .nav-wrapper > ul.cf > li:nth-last-child(1) a").replaceWith($(".search-block"));