The brands mentioned in an earlier answer are the typical, well respected, brands. I used a Leica microscope years ago. When selecting a microscope, you want to look for a "tri-nocular" set up, so that you can have your camera affixed to the microscope while you look through the eye pieces. Microbehunter(dot)com has a discussion on affixing cameras to a microscope.
Before you plunk down $2k for your new favorite microscope, I would recommend a two step approach for in-situ in-wild microscopy. Specifically, Step 1) Get a cheap microscope kit and try your microscopy-backpacking endeavor with the cheap microscope kit as trial-run.
When you do that, your going to run into a couple of microscopy challenges. The first is that you need to prepare the samples to view in the microscope. Like most microscopes, your DOF is wicked-thin. As such, you'll probably need a couple of glass slides so you can squish your subject flat so that it's in focus. You'll need a super sharp Bowie Microtome & Camping Knife to slice your subject to fit neatly between the glass slides. The other option is to buy the George Forman Portable Ultra-Microcryotomy Thin Sectioning Tool & Grill made by Ronco. Ok - I just made that up - there is no Portable Ultra-Microcryotomy Thin Sectioning Tool by Ronco. Actually, there isn't a Bowie Microtome Knife either, so, you'll be stuck with thin sectioning by hand.
Let's say that you get your specimen in the glass slides. Then you'll place it in the microscope and you'll want to turn-on the power to the microscope. So, that will be your second challenge - Power. Why? Because good microscopy, like good photography, depends on light. You probably want to use a variety of lighting techniques to properly illumine your subject. For example, you may want to use a polarized back-light to help bring out certain morphologies of your specimen. To solve this problem, you can simply bring a few car batteries w/ converters to power your microscope. This is why you'll be glad you brought your friends on your camping trip simply because they were willing to each carry a car battery. By the way, you'll owe them for this favor, but not as much as you think. Why? They laughed so hard watching you by the campfire as you struggled to slice a thin section of your specimen with your camping knife, they fell off the log and nearly dropped their beer. For that entertainment, they were willing to carry the car batteries.
Which brings me to the second step of this approach - Step 2) Dont buy a microscope to bring it into the woods. As you can see from my scenario above, it may be easier to bring the specimen back to the lab. The other benefit to this approach is that the police will leave you alone because you didn't steal all the car batteries in your neighborhood to power your microscope. You can thank me later for keeping you out of jail.
PS. There were no beers dropped during the writing of this answer.