Thanks all for the very kind replies.
I've got his belt nearly finished, it's fashioned from a belt of mine (20yrs old) that, while cool and antique looking (and still fits me), isn't something I'd wear anymore. It's the perfect width for him as a kilt belt.

But I've run up onto a problem now dressing my little guy.

Does anyone have an inexpensive option for kids kilt hose?
I thought about soccer socks, but they tend to have the striped cuff.