Just the frame? Used or new?
Usually step-thru frames are on low dollar bicycles and are not generally in high demand. At least based on all the conversation I've heard and seen and imagined in my deliriums.
If it is only the frame you want, and you want new, then look at all the mfr's that offer step-thru bikes and see if they sell the frame only. Otherwise I think you'll have to exhaust all the used sources and probably buy an entire bike then strip and build it to your desires.
I have seen a few step-thru bicycles being ridden around here that looked nice and well suited to the use their owners were using them for. But these were already built bicycles. I think these in particular were from Specialized or maybe Trek.
Last edited by Iride01; 10-25-21 at 09:57 AM.