There is a thread in our Feedback Portal (link here) for a feature request that might suit your needs. If public methods for controlling the grid are implemented you will be able to invoke them from buttons anywhere on the page. I have given your Vote for it. You could also Follow it in order to receive email notifications for future status updates.
Another way of doing it is to use a custom form for editing or adding (for examples click here and here).
A third way could be by relocating the GridCommandButton "Add" by surrounding it in a div and use the position CSS property to put it anywhere on the page where you require. Here is a short sample: