Hypex sells class 'd' semi-kits. Well regarded in some circles and has many of the virtues of there ilk.
You can buy amp modules, PS modules / a transformer and 'case' it yourself.
I have the International Rectifier class 'd' reference amp sitting out in my garage, awaiting case and PS.
My last kit? A Knight Kit Star Roamer short wave receiver, built certainly no later than about '66.