Ugh!!!!!
Well, the RV shop contacted the manufacturer of the tank back in July. They said "we don't make the specific model, but we make a direct replacement". So hooray, it was ordered for some $350 plus $150 shipping.
Fast forward today, the shop has the old one out and the new one isn't a direct replacement. The connections don't line up at all and the exiting mounting system won't work for it. And we're leaving for Yellowstone next Friday.
The shop called the manufacturer, and is waiting on a return call on how they're going to make this right. What a mess.
The only short term solution though won't include a new tank. And spending for at least a few hours labor to come up with a short term solution is NOT something I want to do.