Simply replace your built-in upright freezer with a stand-alone one if your recess is too small to meet your needs. You can use the freed-up space for additional storage, or fit a steam oven and warming drawer into the empty recess.
Make sure that there is enough space for ventilation underneath and at the back of your freezer. This will keep the power requirement down.
A unit front to match your kitchen can be attached to an integrated upright freezer. If your freezer can take a panel, you can slip decor panels into a frame. These will also match your kitchen units perfectly.