Front bag/basket configuration that works with butterfly/trekking bars?
I suggest you look for a bag or basket using the Klickfix system. There are a wide variety of handlebar bags and baskets using these mounts.

The Klickfix mount is about 85mm wide. It is designed to fit either side of the stem, so for a typical stem it needs about 20mm on either side. This section of the bar has to be mostly straight, though the mount will probably fit on bars at a small angle.

Depending on how big a bag or basket you are using and the angle/direction of the handlebars, you may find the curves or ends of the bar get in the way of the bag. If so, you can get the Klickfix "distance set". This extends the mount, so moves the bag a bit further away from the bars. Or you can adjust the angle of the mount, to position the bag above or below the handlebars.