depending on exactly how small the mics need to be. don't forget about the lowly dynamic mic ( even ribbon mics-but they present other issues), which do not require phantom power.
I own a pair of Beyer M201's that I have stealthed many a show with, but they are as big as AKG 48x's, so it's all in the smuggling technique as Greenone says.
That said, I believe there is a thread on here about some DIY Panasonic caps that some folks fashion in to recording devices. I *think* they have a small (lightweight?) power source.