Losing your car keys can be frustrating. Replacing them can be expensive if one of the "keys" you need to replace is the kind of sophisticated microchipped remote control device that is now common with new models. You have three basic alternatives for replacing your keys: your car dealer, a locksmith or a mail-order car-key vendor. The last two options are cheaper than the first.

Car dealer
The dealer from which you bought your car can replace the ignition key and entry key (or keyless entry remote). They simply need the Vehicle Identification Number and your documentation for the car to confirm that you purchased the vehicle from them. Dealers often charge a steep price, however---anywhere between $150 to $350 to replace a remote control device. So going to the dealer should not be your first resort, unless your need is urgent and no alternative is readily available.
Locksmith
To avoid the cost of an expensive replacement from your car dealer, consult a locksmith. An ordinary key may be replaceable for a few dollars. Many locksmiths can also program a keyless remote for you, in which case the fee is likely to be tens of dollars rather than hundreds of dollars. The locksmith will need the VIN to cut a correct key or program a keyless remote. (Since the VIN number can be used to obtain a copy of your remote, it's a good idea to keep it concealed with a bit of tape to help thwart thieves.)
One benefit of AAA membership is coverage for locksmith service if you have been locked out of your car with the keys inside or if you have lost your keys. If an AAA roadside assistance contractor cannot gain entry, AAA will reimburse up to $50 to $150 for a locksmith's parts and labor, depending on your level of membership.
If time is not of the essence, you can purchase remotes from an online vendor like KeylessRide and RemotesAndKeys (see Resources). You will need to supply the manufacturer, model, year and VIN of your car. Programming instructions will be shipped with the remote.
Backup
Whether you've just lost your car keys or fear that you might do so, it's a good idea to obtain an extra copy and hide the extra set in a safe place. Then the next time you lose your car keys, you'll be able to replace them within a few minutes.

 

Thank you for the info, will be very helpful.

 

Additional microchipped keys can be programmed so long as there are 2 already programmed keys in your possession. The owners manual explains how. Right off the bat I go onto eBay and buy a chipped key or each of my vehicles that require them, then have them cut and program them. Most hardware stores I used don't charge to cut them because I bring in my own blank and they can't gayer enter the programming. Doing that as soon as the vehicle is purchased allows my wife to have a key, me to have a key, and a spare in case any is lost. If one happens to turn upsizing, it's just a matter of a few doors and a week to have it replaced.

We recently purchased 2 new vehicles, a 12 F150 and a 12 Fusion. Both of these vehicles have gargantuan keys with the keyless remotes integrated making both keys cumbersome to carry on the same ring. I found on eBay that for $14 I could buy 2 keys in the style of the previous generation f150 and program then to work. This way I carry just the regular key for her car and the integrated key for my truck and vice versa with her keys and the remaining factory integrated keys are spares.