Latitude e5470 laptop backlit keyboard question

I purchased a Latitude e5470 laptop without the backlit keyboard and without the extra tracking ball you find in the center of the keyboard. I just have a regular non-backlit key board and then the tracking pad.

I've only seen the backlit keyboard with the tracking ball included. This does not fit my keyboard slot. There is an extra edge under the spacebar. I want to know if I can now buy a replacement keyboard that has the the backlit feature and fits in my keyboard slot.

Thanks.