Irvine has been interested in adding firepower to his squad since his arrival with Craig Beattie and American Twellman being targets he has bene unable to capture so far.
Brown and Mellor look like being safe to start barring a knock that Brown picked up in pre-season. Whaley has also played as a second striker with Ormerod and Hawley looking like being frozen out.
North is 20 years old and looks like signing for a fee of around £600,000 before the start of the season from League Two side, Grimsby.