That light looks like a standard Malibu light commonly sold by Home Depot back in the 80's so finding a replcementreplacement cover will be almost impossible. The damages done to the lens and socket were caused by the halogen bulbs that were used before the LED bulbs came into existence. Those bulbs were extremely hot. To clean the lense, get some emery paper and light grade oil and rub the lense on both sides. Clean off the rubber seal and add some silicone sealer to the lense and cover. I've also drilled a weep hole at the base for many lights I've serviced in the past. You should be replacing any halogen bulbs with LED bulbs.
In the event you don't want to try to maintain the fixtures, go to your home store and check out what they've got. You can usually get a pack of six for around 80 bucks. They usually come with LED bulbs now.