there are some after market huds available: just go to amazon and search "car hud".
one kind uses the obd2 port, the other just plugs into a cigarette lighter or usb and uses a gps for speed calculation.
i haven't tried them yet, but i've been interested for a while.
i think they all run into some ghosting problems (the front and back of the windshield both reflecting the image), but i'm not really sure how bad those are. an '02 vette i checked out had a hud that was pretty nice with no ghosting, but i read somewhere (a long time ago) that the plastic safety film in the vette's windshield was wedge shape to prevent hud ghosting.
there's also something reallt cheap to turn a cigarette lighter into some usb ports: the "griffin usb car charger" sits almost flush and gives you two ports.