Use a 12 volt sealed beam headlight as a load, and apply power to the X terminal. The P terminal doesn't necessarily need a pilot light attached, it will flash with or without that one connected. 3-terminal flashers are hopelessly out of date. Just get a heavy-duty 2-pin flasher and it will flash up to 6 lights in parallel.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!