Tall, slim uniform(ish) pants for an eleven year old

My daughter has a 23" waist and a 26" inseam. She's currently wearing the size 10 uniform pants, but her ankles are showing and there's an extra three to four inches of fabric getting bunched up at the waist by her belt. She will drown in a size 12.

I purchased a random pair of pants off Amazon that had complaints about the waist being too small, and the waist is still much too big. Anyone have leads on tall/slim convertible (she's firm on this requirement) olive green pants for youth? I'm a reasonably competent sewer, so willing to do some alterations if need be. I'm seriously considering sewing her some pants from scratch, so I guess I'm open to convertible pants patterns as well if you have them...

I searched through the archives but couldn't find any recent threads on the topic.