I think it's part of the Trade Route Maps, but don't quote me on that. Maybe if I told you specifically which maps I had, it'd help matters.

Appendix A: Colonizable Planets
Colonizable planets map
Appendix B: Trade Route Maps
Cross-cloud and Downspin routes
Circle and Short Routes
Nga-Seng and Two-Headed Routes
Appendix C: G'Nunk Warship Manual
Dweenle Transport
Tandelou Scout
Tandelou Transport
Tandelou Warship
G'Nunk Scout
G'Nunk Warship
Humna Humna Scout
Humna Humna Transport
Ng-Kher-Arla Scout
Ng-Kher-Arla Warship
Spemin Scout
Spemin Warship
Uhlek Scout
Uhlek Warship
Umanu Scout
Umanu Warship
Appendix D: Flux Nodes
Flux Node Map
pg 80: Flux Nodes by coordinates
Appendix E: Excerpt from Autobiography of Nergnerj Bemfblunk

I'm assuming the map I'm missing is in Appendix D, but don't quote me on that.