Electrical Install Auxiliary Power Outlet

I am going to install an auxiliary power outlet in my '92 Mustang in addition to the stock cigarette lighter/outlet. Trying to determine the best way to wire this up. The instructions state to wire directly to the battery, as it has its own internal fuse. I'd rather not have it live all the time and have thought about doing it a couple of different ways:

Wire from battery to fuse to switch, then switch to outlet. This way it can be switched off until needed, then switched back off again. The switch would always have power but the outlet wouldn't. Benefit of this method is that the outlet could have power even if the car is turned off.

Wire from existing power source that comes on with ignition to fuse to outlet. Outlet would only work while car is on. If I go this direction, what would be the best source to tap power from?

I'm also open to other ideas and suggestions. Please let me know your thoughts. Thanks.

Um, no. Just asking about the wiring part, thanks.

I appreciate all of your replies. I like your idea of utilizing the spare fuse locations and may look further into that in the future, but for now I tapped in to the blk/lt green wire for ignition power and ran a 20-amp inline fuse. It comes on with the car but I decided to install a rocker switch as well so that I can keep it off for the most part and not have the little blue light shining at me when not in use.

As you'll see from the pictures the reason I couldn't use the two-port plug-in mikestang63 first recommended was because I needed something to fill the hole that I cut in my dash about 17 years ago...ah, youth and stupidity. I had a CD changer with a display and thought it would be really neat to have it flush-mounted in my dash. Well, it looked really cool but within a year someone broke into my car and stole everything, leaving the useless display and hole in my dash. I have been trying to decide what to put in its place for years then finally found this double power outlet that looked like it would fit and appear somewhat stock. I shaved it down then made a small plastic backing to fit the frame. It's not perfect, and may still see some tweaking, but much better than an empty frame...Just need an outlet cover now but surprising those are hard to find. American Muscle sells a nice one with a Mustang emblem on it but for around $25!

Thanks again for all of your thoughts, ideas, and information. StangNet has been a great resource for me over the years, especially your posts Joe.