I've done several adventure races in Arkansas. The terrain is quite nice. I haven't seen a true O-map, but I've been given several maps that were certainly better than USGS. In particular, for last year's Raid the Rock (Little Rock), we got a 1:7500 with 2ft contours that was pretty good. You could try contacting
Team Traveler for a copy.
The closest neighboring map is probably one of SLOC's more southern maps, such as Hawn, S-F, or St. Francios. There are a couple of ROTC groups from NE Arkansas that come to our meets on a fairly regular basis.