Basically you can use any 1/35th scale figures and convert them with a minimum of fuss... It's really just the aid-bag and helmet markings/armbands... Moderen medics are a little difernt because, like you said, the aid-bag has been replaced by that big-azzed trauma kit the Doc humps around.. But the aid-bag was pretty much the same for WW2 and Korea, and then a different model again for Vietnam through Desert Storm..
For WW2, weapons are an issue since medics weren't allowed to carry an offensive weapon (meaning a rifle or SMG) but could carry a defensive weapon (pistol or carbine) for defense of them selves and their patients...
That held up pretty much until the early 80's, when Doc started getting an M-16 along with everyone else.. Even seen a couple with M-203s, once upon a time, lol...