Since you have a factory LED gauge (Ultralite II) I think Autometer will fix dead LED's on their gauges free if you send them in. Call their help line to confirm.
If you want to upgrade a non-LED gauge to an LED bulb look at these.
http://autometer.com/cat_accessorieslist.aspx?pid=27
If you want to upgrade a non-LED gauge to an LED bulb look at these.
http://autometer.com/cat_accessorieslist.aspx?pid=27