How to find different size icon for a certain app on the itunes app store?

I need to crea开发者_开发问答te a widget where different size of an apps icon is needed, how do I find them in different sizes? The only thing I have is the itunes app link like the following

http://itunes.apple.com/us/app/yelp/id284910350?mt=8

1. Use a Regular Expression to find the URL of the image, in this case, http://a1.phobos.apple.com/us/r1000/012/Purple/42/80/fc/mzi.dqbtrgug.175x175-75.jpg.
2. Download the data using NSURLConnection.
3. Use UIImage to resize the image.