Car Alarm Trouble

I can't believe I let this happen for the third time!!! The battery in the hand-held remote for my car alarm died. Unfortunately, the alarm was on when this happened. Which means when I open the door the alarm goes off. And the engine won't start. For a couple years I kept a spare battery in my glove compartment so I wouldn't be stranded. And I'm pretty good about just changing the battery every six months just in case. But it caught me by surprise this time. And it's not like they sell those itsy-bitsy batteries just anywhere. When I finally did hike to Sav-On, they did have the battery, but didn't have a little screw driver to open the remote. AARRGGHH!!! Once again, technology is fantastic when it works. But when something doesn't work out, I feel fantastically irritated and helpless!