The National Geographic "Trails Illustrated" series includes folding water resistant topographic maps of Big Bend NP but I don't know about BBRSP being within the Nat Geo/TI series.
For a completely fascinating BBRSP map experience consider the Texas Bureau of Economic Geology publication #GB0027 (Guidebook 27) Geology of Big Bend Ranch State Park, Texas, by Christopher D. Henry, published by the Texas Parks and Wildlife Press. It's not cheap at $19.95 but it includes 72 pages of text including 81 figures and line drawings with 1 oversize color geologic map in two sheets. It is written with geologists and non-geologists in mind. A companion product is #DE0003 "Down to Earth at Big Band Ranch State Park: Geologic Map and Trail-Side Geology".
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