If you are fighting a cold, it's better to make your own chicken soup. You can't get this out of a can.
In a small saucepan, melt the butter over medium heat. Add the orzo and cook, stirring often, until deep golden brown, 2 to 3 minutes.
In a large Dutch oven or soup pot with a lid, heat the oil, three turns of the pan, over medium-high. Add the onion, leek, celery, carrot, thyme, garlic, bay leaf, and lemon zest. Season with salt and pepper and cover the pot. Cook the vegetables, stirring occasionally, until softened, 7 to 8 minutes. Add the stock and 1 cup water. Bring to a boil over high heat. Add the orzo and chicken. Cook until the orzo is al dente and the chicken is heated through, about 7 minutes. Add the lemon juice; season with salt.