MVC :: Getting File Location In Controller?

I have a controller that returns an image for a given parameter (productID). The image for a product is loaded from the database, but if the product is new, then there is no database record, or perhaps the image is null. In that case, I need to show an image that indicates that no image has been uploaded (e.g., a red X). The code to get the image from the database is straightforward, but the fallback image resides in the ASP.NET MVC application. The problem is, this is fairly generic code, and it will be used with areas later, so I want get the physical location of the file (i.e., "~/Images/noImage.jpb" to full file path). I know how to do this is a normal ASP.NET application, but how do I do this in a controller, in a way that won't break when the application is put in a subfolder?