Start with a 10 amp fuse. If you're trying to flash 4 bulbs at once, that's definitely going to be more than 5 amps. If you're simply selecting a right or left turn, you might draw less than 5 amps, but it's going to be pretty close to maxed out even then. Most fuses need a 20% surge capacity over the anticipated constant load.
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!