Drilling a hole isn't all bad, I usually do it for remote starter. You can drill the hole down underneath the dash around where the pedals are, if you're car is
an automatic there is usually a little spot where the clutch pedal would go and is usually a good bet to drill a hole. Just make sure to install a grommet and put some silicone around the hole to keep water out.
I know you said you didn't want to drill a hole, but just figured I'd put it out there for you
