You could use a tarp attached at the corners and guyed down I suppose. The Camperlands one mentioned above has side screens that attach, i've just got the normal sun canopy but not used it yet.
I've got the Camp-let sun canopy and am not very impressed with it to be honest. It collects puddles of rainwater, and looks a bit sad and saggy to me. I'm pretty sure there must be a more cost-effective solution.
The day room is very versatile as you can zip up all four sides so it looks like a gazebo. Features include 4 Roll up Doors, two covered PVC Windows, Two covered mesh Vent Windows. Most sellers include canopy poles so you can turn any one of the four doors/openings into a sun canopy.
It comes with a groundsheet, ( we don`t use ours).
Not been charged to date, but some sites do. Just tell them you have a gazebo as trying to explain what a day room is sometimes is like trying to explain you have a TT/FC and end up booking it as a tent as it easier.
We check before we book to make sure we are not charged.
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.