I'm pretty sure there is a continuous 12v feed in the fuse box...
there is certainly a keyed 12v there.
cos I use it
The bad news is that to get at the fuses, you need to be able to bend in half backwards, see in the dark (not enough room for you, and the fuse, wire AND a torch...), and expect to break the Honda fuse puller (which is situated in the fuse box under the bonnet BTW)
What I did was use a multimeter, set the key to where I wanted it to provide power (II), then pull each fuse in turn and check for current.
The turn key off, and make sure current went off too (obviously you don't want that to happen for one of your feeds).
make sure you test both sides of the fuse - one side is obviously downstream, so won't have current unless the fuse is plugged in!
Then (and this is the tricky bit) put the wire from your accessory into the fuse holder (downstream so it's protected by the fuse), and put the fuse back in - forcing the wire into the holder.
It's not the most technical of solutions, and you need to be VERY careful not to bridge the 2 fuse connectors with the wire!
but once done, it's done
Alternatively, for the keyed 12v, go from the cig lighter (only one bit of trim to remove), and feed the wire down the side of the tunnel towards the front of the car (it's nice and tight between carpet and trim, so will hold the wire in place), then run it under the steering column and to the door rubber trim.
Pull the door rubber off, put the wire in place, and cover it back up with the rubber trim again