Turn Signal Indicator

Often the glass with break free from the base when you try to turn the bulb, just like a home light does. You need to push the bulb into the socket before you turn ccw 1/4 turn. This "push first" might be the trick you are missing. If only the glass turns, go ahead and remove it, then use needle-nose pliers to get the base out.

Auto parts stores used to sell gasket material. You might make your own with a bead of RTV. Put clear tape or such down first on both surfaces so the RTV doesn't stick, then use the two surfaces as a mold. When it cures, you have a silicone gasket.