The NSCursor
documentation lists a number of resize cursors, but they are all of the variety used to resize panes inside of a window: NSCursor Reference
How do I get the resize cursors which OS X uses for resizing window borders?
(I.e., the arrows without the bar in the middle.)
Duplicate of Native OSX Lion resize cursor for custom NSWindow or NSView
See particularly the second answer, with Retina images.