Semroc sells a clone of the Mark II
Here is a list of the Estes first 10 kits
K-1 Scout
K-2 Mark
K-2A Mark II
K-3 Space Plane
K-4 Streak
K-5 Apogee 3
K-6 rAnger
K-7 Phantom Original BT-20 no fins
K-7B Phantom BT-50 with fins
K-8 Sky Hook
K-9 Sapceman
K-10 Cobra

From what I understand, the Mark was part of Model Missiles and G Harry Stine. If this is not correct, please correct me.