Awhile back I did a commercial for a hobby store. I could have used that
for a model train shot. (The camera recorded entering a tunnel and the look
of pure enjoyment of a boy seeing the train coming out the other side)
I used one of those memory card cameras being sold at Walwart mounted on a model flat car.
Usually medical cameras use fiber optic bundles and the other end of the cord would be loaded
with the support electronics.
About 15-20 years ago, Lionel had a camera in a locomotive. The lens was where the headlamp would have been. It was B&W and transmitted the video on the tracks where a capacitor-isolated balun took the video to the TV set.
On the OP - I sure wish that they were available five-years ago when I was undergoing quarterly ERCP's (Endoscopic Retrograde Cholangiopancreatography).