Many of Warlord's plastic kits are upscaled 1/72nd ones made by Italeri. In my experience the scale of the tank commanders vary due to this process - with say the Tiger II one being huge.
Similarly however the vehicles are around 1/56th scale. So the hatches are a bit tight for most 28mm models. Though a bit of trimming around the waist tends to work. I'd recommend picking up the Rubicon crews. Or other companies like Die Waffenkammer do some. Warlord have a few as well, though personally I find the poses a bit static or awkward.
If you can get a hold of them, the crew which come with Rubicon's Sd.kfz 222 turret kit (able to be bought seperarely as an upgrade for other vehicles - which come to mind would do for the more common variant of the Puma), are just gold. Their poses sitting on the lip of a turret's hatch or vehicle's side set them apart from most of the tank commander models out there. Only Bad Squiddo Games Soviet tank commander set comes to mind with a similar pose.