We have a key with a chip in it but want to buy an additional key,

Holy &@€! When I lived in the US Home Depot wanted $75.00 and I thought that was outrageous. Try Sears, Lowe's or any hardware store that cuts keys. Not all can do keys that have chips just shop around. If your vehicle requires a chipped key a regular key won't work to start it. You can only unlock the doors.

Try local locksmith they negotiate to remain competitive. But no you cannot start the car without a chip key