The K-planes that used to get fitted to the smaller Phantoms (with the motor/pump mounted just behind the tab, directly on the transom) were disscontinued a few years back, I can't remember the model No, but I bought an 'old stock' set from Doller Offshore in Ft Lauderdale about 3 years back, and they were very rare back then!
OK, found the No, they were 'K-Plane 110S' and were quite regularly fitted to the P25 race boats, so would go easily on a single motor 21 or 23