Originally Posted by
BrocLuno
It takes some planning. In my case a lot of looking for a suitable step-through frame in aluminum with an 1-1/8 inch threadless steer tube. Not that common in "womens" bikes.
My wife's bike is a mid-2000s Trek 7100 step-through. It's aluminum and has a 1-1/8" headtube. It comes with a threaded fork and quill stem, which is pretty uncommon for the 1-1/8" size, but can easily be changed over to a straight tube fork with threadless headset if desired. Not exactly turn-key if you convert, but the bones are there.