Welcome to the Figure-bashing world...
First, start looking any pictures you can find of just how German infantry looked riding in the back... Some will be hunched over in conversation, some will be standing, at least one will be on the gun...
Then the fun begins... Start collecting figure sets and learn some surgery, my friend... Actually, it's not as hard as it sounds, you just gotta do some cutting and filling on the figures... Get the poses figured out one area at a time... I usually assume the poses myself, making mental notes of where my legs are pointed, feet, etc... First, get the lower half to fit (the seated figures in the Tamiya 8-ton Semi-Track figures are a good start), then the upper torsos.. You may have to cut it mid torso to get it to lean over right, and then fill the gaping hole in it's back, and extend the Y-harness with tape.
Then you'll dig through arms, trying to find sets that look natural, but you'll end up cutting at the elbow here & there.. Then it's time for the heads..
Once they're all posed right, start filling the gaps and then it's time for paint.. The best way to pose these guys is to drill opposite holes in each part and insert a wire, like a straight pin (or paper clip for torsos).
If you can't find the figures you want, I'll do a quick one and post it to show you how I bash figures...