Not a 28, but, hammerless. Would this work?

https://www.gunbroker.com/item/966015473

I have the 12 gauge version. Not a kid gun, unless he is a masochist.

The 28 gauge version of the Companion is a bit off the charts:

https://www.gunsamerica.com/903335678/J-L-GALEF-COMPANION-FOLDING-28-GAUGE-SHOTGUN.htm

Best,
Ted