CG,
Looks to be about $275 for a replacement. I'll bet Ritchie can replace the UV damaged plastic bits (clear 'globe', black frame and possibly the red card) for less. I would certainly get the white plastic UV cover to prevent UV damage in the future.
Sadly, most our sailboat gear just sits out in the sun getting faded most of the time. I've become a big fan of covers to prevent UV damage.
Mark