Key clones...

Depends on what car you want to use it with. And even if it works with your car, you might need special equipment to "teach" your car to recognize it.

Perce

You can get remotes for most cars quite cheaply, designed for specific cars. They even look like the original.

You can also get directions for most cars, but probably not all, on how to program them yourself. Just google, fob installation instructions.

I forget the url but one or two guys have instructions for most cars.

And when you buy the remote it will either have instructions or give you the url. Put your make model and year of your car into Ebay and it will tell you if the product is meant to work with your car.

Key blanks too can be bought cheaply for most cars.

So I have 4 sets of keys and remotes for my Toyota and I also did for the Chrysler Sebring I had for 2 months. 2005 and 2004.

OTOH, if you want to have these cheap ones around just in case and you don't know what car they're mant for, they might work