I had my eye on those Audio Mirrors - you beat me to them! Actually, I already own a JAS Bravo 2.3 that uses the 6C33 as an SET and sounds great, although the build quality is less than optimal. Right now it's blowing fuses. :-(
This guy advertises on US Audio Mart on a regular basis and ships from New Jersey:
Also, Ralph Karsten used to build amps that use the 6C33 so he might have some in stock.