https://legendsofkansas.com/cherokee-neutral-land/ has a map...

https://digitalcommons.law.ou.edu/cgi/viewcontent.cgi?article=2927&context=indianserialset This is the most comprehensive discussion contemporary to the events surrounding the Neutral lands I have come across.

A pre-war NYT article that is quite lengthy discussing the neutral lands is here:
https://www.nytimes.com/1860/11/07/archives/kansas-a-new-page-in-the-history-of-the-territory-the-trouble-on.html

https://www.kshs.org/publicat/history/2007autumn_cheatham.pdf
An article about Southern Cherokee's in Kansas and the war with several good maps. I think the strip that is being referred to in the raid accounts may be marked as the Quapaw Strip on the map on page 3 of this article. It roughly fits with what we know about Blunt's movement chasing Mathews and the fact Mathews had the recruiting order for the Quapaw on him when killed.

JJR