I was browsing phones on Amazon yesterday and I saw the Nokia 1 there, sold by Amazon (not a third-party seller; it was priced at $59, IIRC). Nokia.com doesn't show it as being available in the U.S. so I'm wondering how well it would work with T-Mobile. (I'm also a little surprised to see Amazon itself selling it since it's not officially available in the U.S.)
Nokia has not been marketing to the US customer and their phones are not designed for the US market. If you decide you can't live without a Nokia 1, be sure to get the Latin American version. It has some compatibility with T-Mobile's LTE bands.