For porch lights, Home Depot has some large LED flame bulbs that are pretty good and have a sensor inside that makes the flame always point "up" regardless of which direction the bulb is screwed in from.

Depending on how much space you have to work with in the lantern, these are small incandescent bulbs that flicker, but don't throw a lot of light, or if you wanted to go LED, GE (and others) make flame shaped bulbs in either the narrow candelabra base or the wider medium base, depending on the socket you'll be working with.