Forgot to add optical drive to order, easiest/cheapest fix?

So I excitedly ordered my new latitude 6400 yesterday only to realize that, after adding everything else I wanted, I forgot to add an optical drive.

Now, I need to accept some responsibility first and foremost for not noticing, but seriously, why the heck is "No optical drive" the default option!?!

Seriously?!?

Now I need to fix this. Should I

1) Cancel the order

2) Buy an external

3) Get a compatible drive somewhere else

Ideas?

Thanks,