As a sub-note, a group of 12 new armored ships (Kreuzer P ), successors to the famous Admiral Graf Spee , Admiral Scheer and Lützow , were part of the German Z-Plan. The design studies for the three battlecruisers of the O-class (Schlachtkreuzer O, Schlachtkreuzer P, Schlachtkreuzer Q ) were simultaneous started to those of the new Panzerschiff design (Kreuzer P ) in 1937.
In 1939 it was considered to replace three of the Panzerschiffe with the same number of this new battle cruisers. Construction orders were given to Deutsche Werke, Kiel, the Kriegsmarinewerft in Wilhelmshaven and the Germaniawerft in Kiel in the same year, but none of the ships were started.
Those ships were planed with the idea of the war against commerce as a priority but with sufficient armament for combat with 9 x 11" main guns. Therefore, they should get a mixed propulsion system, diesel engines for long range medium speed cruises and additional turbines for high speed combat action. As the main task for of these battlecruisers was to engage enemy convoys and destroy transports and cargo ships, in difference to the heavy protected H-Class battleships, they would have armor protection of a cruiser only. So it's very doubtful that one of these ships would have been able to attack a well protected allied convoy with any great success.
Only one kit is available of this speculative design and that comes from Russia. HNV produce the 'Schneidheim' (A name not mentioned as being intended in any source I can find) at 1/350 scale but at a high cost of £140 (equiv) plus shipping.