UNDERCOVER CAMERA SUPPORT
You say your biggest problem is going to be keeping your camera steady, at long shutter speeds, in places that are so dark you need radar to get from one end of the room to the other. Flash is forbidden and tripods get confiscated on sight?
The Walking Stick Monopod, aka "The Merlin Stick".
Click image for larger picture.
Ok, I got the idea after wasting money on the most useless gadget I've ever bought -a shoulder stock. Then I started wondering about other ways to fix a camera firmly, and one thing kind of led to another...
I've dedicated long hours to finding ways of bending silly rules aimed at preventing me from getting my photos.
Buy a wooden walking stick, the longest you can reasonably carry.
Make sure it has a wide grip on top.
Drill a 5mm hole vertically through the top of the grip, and wind a piece of 1/4 inch threaded metal into it far enough to leave about 1.5 cm sticking out the top.
In your pocket, carry a small ball swivel head. Like James Bond, once you're inside you just attach the swivel head and BINGO! You have a monopod! Not quite as stable as a proper tripod, but you'll get your shots! (Q would have thought up something more effective...)