Helping out a friend who needs one…
try yaqui. i have a 48(with 650s) and i know ves mandaric makes larger ones. i’ve had mine for nine years and still like it a lot.
peggy
You might want to look at the Cervelo RS in the xs size. It’s an awesome little bike.
Greg.
Orbea? Not sure it is exactly a 50, but it must be pretty close.