Having just done a (UK) market search to recommend a bike to a small woman (4'11"), I found that one or two of the Treks come in a 43cm w/ 650c wheels. The effective top tube is about 48.5cm - so lovely & short. It's not intuitive or very clear which bikes come in this small size - but if you go onto the Trek site & go through all the road bikes, you will see most come with 47cm as the smallest - but a couple come smaller.

We frequently have small women customers (as a 5'1" myself I know the frustrations) & there aren't a lot of off the peg 650c bikes available in the UK - sometimes you can find a 43cm Cannondale on ebay - but I dont' think they make one new anymore.