AKICODW: sewing pattern for bike-riding jumper

So at one point in my life I lived in Madison, Wisconsin and I bought some jumpers while I was there. They look like a button-up sleeveless dress (princess-seamed) with a wide/draped skirt, but the skirt is split so that it's possible to safely and comfortably ride a bicycle. Years have passed, I've gained weight and I'd need a minimizing bra to fit into the top of these dresses. Now I've got a sewing machine and I'd like to find a pattern to duplicate the style of the jumpers, and I'm turning up flat nothing with Google. Anybody ever seen something like this, or am I going to have to get some tracing paper and use the old dresses as templates for a newer one?