A place to start for boondocking sites is
www.boondocking.org. You get to their "database" page, and put in coordinates for the area you are interested in. There is a map at the bottom of the page that shows some lat and long lines. Put in an estimate of what the whole lat and long lines are (38 for degrees north, and -106 for degrees west), then put in a search radius. I normally start with 150 miles, then narrow it down if I need to.
Unfortunately, there are not lots listed right now. I put in a few, as I have the time to enter them. All that I put in, you could get a TM there, unless I specify it is a very tight fit. I have a 2417 Sport, which is 6" narrower than most TMs.
As for being within an hour of Aurora, it will take at least half an hour to get to C-470 and Hwy 285. I go up 285, as it has less traffic. But, I normally go over Kenosha pass, into South Park. Many places (Lost Creek; west of Jefferson; west of 285 about 5 miles south of Fairplay) in that area. Part of the fun is exploring. But, in those areas, we shoot our pistols with no issues of neighbors. You can be pretty isolated up there.