Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Parsing through the above, the simple recipe becomes:

base oil: 80% Canola (alternatives are listed)
hydroxy fatty: 13% Caster Oil
wax: 7% Lanolin (also mentioned are jojoba (which is preferred) or meadowfoam)

All 3 oils are easily obtained (Whole Foods sells pure Lanolin for example).

For the wax they prefer jojoba.  I picked Lanolin as it is closest to lard in my experience. Lanolin is much thicker than jojoba (I've never experienced meadowfoam).
I remember reading a 2009 post from "kevininasia" and his experiment allowed Tallow to reach a level of 5% in his motor oil mix.