It might be a bit hard on the tipup, since the stiffening braces are in the way of just putting a simple fan on the inside. Putting a really small fan aft of the stiffeners is a possibility, but they may not be sufficiently powerful to do any real good for defrosting/defogging. There is not a lot of space between the stiffeners and the panel, and at that location you are back a ways from the leading edge of the canopy bubble.
After you start the engine, wouldn't there be sufficient airflow from the prop to defog?