Can't help you with maps and such but there is one way that you might be able to find these sites with a little luck and a lot of walking.
An old style throwback way to find sites like this.
This is the personal website of a super nice guy called KCSteve...
http://kcsteve.wixsite.com/kcsteve/blog
A cheap site that is slow and buggy but well worth the time spent there reading about his adventure I can assure you.
He came and spoke at one of my club's meetings a few years ago when I lived in Kansas, talked about what he does, how he does it and answered all our questions plus he brought tons of what he has found and I can tell you this guy was impressive.
He has been doing this hobby for over 35 years and for the last few decades he has specialized in looking for long lost tradeposts and civilian and military campsites...Dragoon sites especially.
He gets permission from huge land owners 100% of the time and looks for old camps on sometimes fields and farms but also sometimes way out in the middle of nowhere on still wide open lands that might encompass hundreds if not thousands of acres.
He uses all the modern tools he can to locate possible sites, the web, old maps, any history about troop movements plus any info he can find at the libraries to narrow down his search areas but all of that can only get him so far.
Sometimes, many times the only thing he can do is get on a huge piece of land and start walking and many times he walks for many miles on those open plains.
He swings his detector as he walks and listens and if and when he gets to a spot where he finally comes across metal he stops and examines that area better.
If he sees signs of the right kind of metal targets he has learned to look for so well, nails, horse tack and other things plus ash from campfires he starts to dig.
I asked him how many miles he has walked doing this and he said he couldn't tell me but it was much more than even he would like to know and uncountable hours swinging that coil hearing nothing as he walks over these vast areas.
All in a day's work it to him though, despite all the wasted time it was all worth it once he came across a long ago forgotten and now totally hidden and buried campsite.
He has discovered dozens of sites over the years doing it this way, sometimes this is the only way to accomplish this and you need to wrap your head around spending the time and effort finding great sites this way if you want to be as successful as he has been.
