98 Lumina Automatic Door Locks?

My Lumina has power door locks, no remote entry. Its a stock Hertz rental, basic model. My 96 Grand Prix has power locks that lock when I shift into drive. It works so well I forget to lock doors on Lumina. Is there an easy way to add this feature to Lumina, Auto Alarm store suggested I install new anti-theft alarm system with that feature. I hope there's a better solution. Thanks

I might want one of those too, my dad has one em on his 2000 Explorer and it would be nice on my lumina:iceslolan