Locating a map

I'm trying to locate a hand drawn map done in 1847, "El Plan. 119 miles from distant from Vera Cruz Mexico." It gives the location of Lt. Thomas Davis's grave and I'd like to use the map as an illustration in a forthcoming work.

David Nevin's Mexican War (Alexandria, VA: Time Life, 1978), 145, cites as the source as "Courtesy Dr. Carl S. Dentzel Collection.” There are three repositories for Dentzel collections--California State University, Northridge; the Autry Museum; and the Huntington Library. I've written to CSUN's archivist and she has no record of the map. Searches in the Autry's catalog don't show anything, and the Huntington's holdings are strictly black and white photos.

The website "Latin American Studies" reproduces the map (https://www.latinamericanstudies.org/plan-rio.htm), along with a photo of the site creator at what he purports to be Davis's unmarked grave. The site creator, Dr. Rafael de la Cova, died in 2018, but in the hopes that somebody is monitoring the site I've sent an email.

Should anybody know anything about the map's whereabouts, I'd greatly appreciate your sharing that with me. Many thanks.

Rick Herrera