Just google or ebay search 'campervan awning' you will find plenty to choose from. Cheapest & as good as any will be a tunnel awning. To fix the awning to the side of a T4 Caravelle you will need awning suction clamps. Get them from the justkampers website, they do awnings as well.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.