No experience choosing a seat for kids, but if I was needing to find one, I'd try the local shop to see if they had any "take offs" that might be tried-and should be cheap if you find one that works. Also, if there is a local co-op, or bike club, try there also. After all, I'm sure most of us here have some seats in boxes that didn't work for us, but might be fine for someone else.