maptools.com** sells a bunch of nice ... well ... map tools, including roamers. More importantly it has great how to's on how to use them.
One other bit of navigation advice ... if using a GPS bring along plenty of extra batteries. I once had to borrow a few batteries from a Girl Scout while trying to show them how a GPS works (Mine died and I forgot to bring extras). That may have been in my top 10 most embarrassing moments in life.
**I have NOTHING to do with this web site - financially or otherwise ... just a happy customer.