There is a grommet behind the glove box. If you remove the glove box, you should find a plate with relays on it, behind that is a grommet which goes through into the engine below the battery.

If you use that, make sure you re-seal any holes you made in the grommet, or your footwell will be full of water soon.

You should then be able to run the wire along the side of the car, under the carpet, remove the side bolster on the rear bench and run the cable through there, or, under the seat bench into the boot area.

Then, drill a small hole in the spare wheel well, grommet and voila, although I think there already is a hole in the boot floor for the fuel pump (that's where the wires to the trip switch go), so you might be able to use that, or enlarge it slightly.

You might also be able to run it under the car, zip tied to the brake lines for example - much easier, but not very well protected.

Make sure you use grommets everywhere cable goes through sheet metal though.