I did see some small Bontrager compact bars at the local co-op recently. I didn't measure the width, but probably in the mid to upper 30's, but very little depth. Full 31.8 clamp area.
Of course, hopefully the OP came up with a solution months ago.
One thought, however, some people tend to think that wider bars give more stability, to a point. It might mean that young kids can do fine with a bit wider bars, then slowly grow in to them.