It can be difficult to find vintage mixte and step through frames that are large. But there are a few new production ones to look at.
The Buena Vista comes in 58cm and 62cm sizes.
https://www.somafab.com/archives/product/buena-vista
https://www.somafab.com/archives/pro...disc-frame-set
Rivendell also has the Clem Smith Jr in larger sizes, with a bit more of casual styling.
https://www.rivbike.com/products/cle...noon-pacific-1
Probably more out there too. Or you could go full custom.