How can I add an additional object to the results of a LINQ query?

public IEnumerable<ProdPriceDisplay> GetShopProductsPrices()
{

    //ProdPriceDisplay ProdPrice = new ProdPriceDisplay();
    var Products = from shop in db.SHOPs
                   select new ProdPriceDisplay
                   {
                       ProdPrice = shop.S_NAME + " - £" + shop.S_PRICE
                   };

    // *** Want to add something like this:-

    //  Products.Add new ProdPriceDisplay { ProdPrice = "some additional text"; }

    return Products;
}

public IEnumerable<ProdPriceDisplay> GetShopProductsPrices()
{
    var products = from shop in db.SHOPs
                   select new ProdPriceDisplay
                   {
                       ProdPrice = shop.S_NAME + " - £" + shop.S_PRICE
                   };

    return products.AsEnumerable()
                   .Concat(new [] { new ProdPriceDisplay
                           { ProdPrice = "some additional text"; });
}

var productsAsList = Products.ToList();
productsAsList.Add(new ProdPriceDisplay { ProdPrice = "some additional text"; });

return productsAsList; // As your return type is IEnumarable, that won't be a problem;