Hardware Made Easy!
Various
2", drain valve, the same drain valve that comes as original equipment on many water heaters, will fit all makes, select the valve that is long enough to clear the insulation between the jacket & the tank.
Genova Products Insert Fittings Steel Insert Coupling
Tigre USA Reducing Male Adapter (Reducing Mipt x Insert)
Tigre USA Reducing Male Adapter (MIPT x Reducing Insert)
Master Plumber 1/3-HP Sump Pump Zinc & Plastic
Fernco Proflex Shielded Specialty Coupling