"Add" Icon for iOS Button

I'm developing a WebApp for iOS, and I need a "a开发者_C百科dd" icon for my button. Something like this:

http://www.winsupersite.com/content/content/127266/reviews/mobileme_iphone_rtm_16.jpg

The button I already have, what I need is just the "add" icon like that.

UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd 
                                                                           target:self 
                                                                           action:@selector(addButtonPressed:)];
self.navigationItem.rightBarButtonItem  = addButton;
[addButton release], addButton = nil;

This will get the framework to add the + icon.

Sorry I've read over the WebApp bit, just use an image.