add the following to your theme’s functions.php file or add it to a plugin, whichever you prefer
<?php function sc_fix_admin_bar_search() { ?>
<style>
#wpadminbar #adminbarsearch { float: right; height: 18px; padding: 3px; margin: 0; width: 215px;}
#wpadminbar #adminbarsearch .adminbar-input { width: 215px; height: auto; float: left; font: 12px Arial,Helvetica,sans-serif; color: #555; text-shadow: 0 1px 0 #fff; border: 1px solid #444; border-color: #808080 #686868 #686868 #808080; padding: 2px 75px 2px 6px; margin: 0 3px 0 0; background: #ddd; -webkit-border-radius: 10px; -khtml-border-radius: 10px; -moz-border-radius: 10px; border-radius: 10px; -moz-box-sizing: border-box; -webkit-box-sizing: border-box; -ms-box-sizing: border-box; box-sizing: border-box; outline: none; }
#wpadminbar #adminbarsearch .adminbar-input:focus { -moz-box-shadow: 0 0 5px #DDD, 0 0 3px #DDD; -webkit-box-shadow: 0 0 5px #DDD, 0 0 3px #DDD; box-shadow: 0 0 5px #DDD, 0 0 3px #DDD; border-color: #DDD; }
#wpadminbar #adminbarsearch .adminbar-button { font: normal 12px Arial,Helvetica,sans-serif; color: #ddd; text-shadow: 0 -1px 0 #444; cursor: pointer; float: right; background: #aaa; background: -moz-linear-gradient(bottom,#6e6e6e,#515151); background: -webkit-gradient(linear,left bottom,left top,from(#6e6e6e),to(#515151)); -webkit-border-radius: 10px; -khtml-border-radius: 10px; -moz-border-radius: 10px; border-radius: 10px; border: 1px solid #808080; border-color: #808080 #686868 #686868 #808080; padding: 2px 13px; margin: 0; width: auto; height: auto; position: relative; top: -22px; top /*\**/: -21px\9; *top: -21px; }
#wpadminbar #adminbarsearch .adminbar-button:active { background: #555555; text-shadow: 0 1px 0 #444; background: -moz-linear-gradient(center bottom , #555555, #3E3E3E); background: -webkit-gradient(linear,left bottom,left top,from(#555555),to(#3E3E3E)); -moz-box-shadow: inset 1px 1px 1px #222; -webkit-box-shadow: inset 1px 1px 1px #222; box-shadow: inset 1px 1px 1px #222; border-color: #111 #222 #222 #111;}
#wpadminbar #adminbarsearch .adminbar-button:hover { color: #FFF; }
#wpadminbar #adminbarsearch .adminbar-button::-moz-focus-inner { border: none; }
</style>
<?php }
add_filter('wp_head', 'sc_fix_admin_bar_search');
?>