I made it myself, its based on the ones used in the film El Cid, so I can't vouch for the historical accuracy
Well, I don't think anyone today can know how the banner really looked
But still, thanks for your offer, but I'll steer away from the movie, as it represents a very peculiar interpretation of the story of El Cid, namely that of Ramón Menéndez Pidal. I'll follow the approach of Richard Fletcher, put forward in his marvelous book
The Quest for El Cid.
However, your banner does look good!