Roger Zelazny published a simple map of Amber and the nearby areas (Mt. Kolvir; Garnath; the stairs to Rebma) as part of the original serialization in Galaxy magazine. The map appeared in Galaxy, Volume 39, No. 2, pg. 101. Thanks to one of the members of the Amber email list, I've gotten a copy of this map. Here it is.

Roger Zelazny's offical map of Amber