is there a constant power source when car is off?

im wiring a flashing led to resemble a alarm system. and because i need this led to be on when the car is off, is there anything i can tap into without wiring to the battery and having to add another fuse? i know some cars have their 12v car outlets powered when the car is off but not our tl's! :( ill be wiring the power to a switch that i can turn on or off inside the car and the led will be mounted under the windshield. i have a base model 2003 tl

another thing is, what size fuse would i need for just 1 or 2 small led's if i go that route and get a inline fuse. thanks guys!