Strongly support using Chinook Medical. They allow you to buy only what you need to replinish or build a kit. The VERY BEST thing you can do is NOT buy a pre-packaged kit. It lulls you into mistaken beloef you kmow how to use all the stuff. It has stuff you don't need and. Don't tonspend precious ounces hauling around. It doesn't have stuff you do need. Finally, if you build it, you will have a personal interest in what's in it. This will cause you to be more interested in checking it after a trip and improving it for the next trip. One tends to treat a bought kit with a set-it-and-forget-it mindset.
X2 RMI, I can personally attest to RMI for training and supplies. Would recommend them as a resource, when I decided to go remote medicine (REMT-B) they had a bridge course with top tier training and certification. When piecing together kits I use a multitude of sources for personal and professional uses. I also agree build and purpose you're kit for what you expect to see and skill level. Dont waist weight on something you do not know how to use.
I really like www.theactivityusa.com for trauma kits and supplies. One of their kit is in the Expo Portal Holiday Shopping guide right now. Pretty cool as it mounts to your headrest in the vehicle and is a tear away for quick access.
+1 for North American Rescue, Adventure Medical, and Rescue Essentials.
I visited NAR's facility in SC in 2012. Super friendly people who were more than happy to show me around after I dropped in without calling. I was on my way back from Southeast Overland and had to check it out.
Adventure Medical's "Weekender" kit is one of the best kits for the money. Supplement it with some extra OTC meds and for about 65 bucks, you can treat just about anything. And it comes with Dr. Weiss' book as well. Hard to beat. I have several.
We have a BIG Adventure Medical Kit (their Marine 2000) which we augment with medications (prescription and OTC) and things like CELOX.
One of my concerns about third world travel is the availability of sterile instruments, sutures, needles, etc. I've been carrying my own stuff with me for 20+ years - fingers crossed, haven't needed it yet.