You might look on eBay or another online store or even in the back corner of a LHS...find the old Tamiya British Stretcher Party (35106) or the British Land Rover Ambulance (35082). Those litter bearers and doctor can be great starts for what you're looking for! With a little putty and some creative sculpting, you can make them any nationality/military you want!
I modified those figures to be WWII US Army medic (foot of litter), ambulance driver (left side) and doctor (right side, holding plasma bottle) at an Aid Station. (It's a work in progress)


The doctor's apron is masking tape. The stethoscope is wire. Plasma bottle is part of a clear styrene sprue with wire and masking tape details. All the rest of the conversions from British to US uniforms were made with putty. I did modify the pose of their arms--except for the medic.
Just an idea. Hope this helps!