I use the Warren, Gorham & Lamont manual entitled Bank Internal Auditing Manual. You can get it from RIA, Customer Service Department, 117 E. Stevens Avenue, Valhalla, NY 10595-1264. The phone number to place an order is 1-800-950-1216. It covers most areas that I need to look at, and is pretty thorough. It comes as a hard copy and a set of disks for the computer, is periodically updated, and should be in your price range. In addition to it, I also use the OCC Examiners Handbook and the Compliance Manual.
Good Luck!