Can't help with sperm oil except that my father had a small bottle of it when I would watch him clean his guns. As Chuck stated, in the 1970's the United States banned all sperm whale products.
As a substitute try Jojoba oil, from the jojoba plant (simmondsia chinensis) and Simmondsia californica, it is a wax ester and not technically an oil.
I am not a chemist but chemically it resembles sperm whale oil or spermaceti oil. Jojoba esters are composed of straight chain alcohols.
A quick Google:The acid and the alcohol portions have 20 or 22 carbon atoms and one unsaturated bond. It contains a 60% mixture of wax esters, including fatty acids and alcohols of chain lengths C20 to C26 (eicosenoic and docosenoic acid, eicosenol, docosenol, hexacosenol), nitrile glycosides (simmondsin and cyanomethylene derivatives). "In 1977 domestic commercial jojoba oil cultivation began because it is the natural substitute for spermaceti, which in other cases has been replaced by synthetic products."
Jojoba oil seems to have a long shelf life; "it will never break down or go rancid." It resembles human sebum; the natural coating our body produces to protect the skin and keeps it supple.
