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ffhound: This annual "event" is coming up...
https://dailygetaways.ustravel.org/ComingSoon.aspx
You might want to sign up to keep your ear to the rail. No cost to get on the mailing list, but it takes a certain disposition to enter the the fray. Unfortunately, the offerings have gotten slimmer and slimmer each year (IMO) and thus can be hit or miss as to having what you're looking for.
There is a thread about it on this board. It will become very active as the starting date approaches.
[I have no connection with them.]