Hey there forum, new member here. I'm glad to see there's other BC fans on these forums. I also have tickets!
I've heard good things about DSM microphones, but I don't know much about them except they're very concealable...
http://www.sonicstudios.com/Schoeps is another good brand, but waay pricey (thousands of dollars). Other than that, i don't know of any other stealthable mics...although if you really want to push it, look at a Sony ECM-ms907.
MiniDisc is the economical and most practical way to go if you just want this as a one-off recording rig. You can get one for around $85-90 for a sony net MD. The only problem with Sony MiniDiscs is that you can't adjust the mic/line input level on the fly (which Sharp MiniDiscs CAN do..see ebay).
To be honest, I wouldn't bother trying to tape the show, there's going to be a lot of security there due to the fact this is going to be filmed for inclusion on a future DVD release. But, if you do decide to sneak it past security, make sure you have some high quality, concealable mics and a small MD at least. Your best bet for stealthing position is ideally center balcony, but if they have the bar open, you're giong to pick up the "ring" of the cash register constantly going off. Another good spot would be against the wall in the back, or on the middle of the floor or as close to either stack as you can get.
Metro isn't exactly known for sound quality though when it comes to stealth taping, but if you can pull off a good recording, that would be cool.
-feel_the_funny (ChoobieWoobie)