Good Map Recommendations for PNG?

I'm planning a trip to PNG that would involve trips to some of the mines in the Ramu and Madang areas and need a map to get the lay of the land --what kinds of roads there are, distances, that sort of thing. Does anyone have recommendations of the most detailed, accurate maps out there?

Thanks!

Many local bookstores carry good topographical maps of the area. You can also find some good ones online. A lot of them are out of date though...
Try here:
http://www.ga.gov.au/nmd/products/external/png.htm