Look here:
http://www.mkbattery.com/content_con...page=locations
http://www.enersysreservepower.com/s...&type=security
http://www.enersysreservepower.com/s...ype=electronic
Then call the head office or distributors' locations in Missouri and check their stock for the FIRST-legal batteries (MK ES17-12 or EnerSys NP18-12). And as for Newark (an EnerSys distributor), call right now; they're a huge electronics vendor, and probably have 24-hour customer service. All three are a drivable distance from downtown St. Louis. They might even deliver.
A hotel will usually accept a delivery for you if you arrange it with the concierge/front desk; as for the Dome, I doubt it, but you can ask.
You may need to top up the charge before you use it.