Falls sich seit dem nichts mehr geändert hat, dann gibt es keine gebräuchliche Abkürzung im Englischen für s.o.

I agree with neufelder.

see above, no abbreviation

vid. sup. (i. e. vide supra) is occasionally used in English, but almost exclusively in academic texts and since, like "see above", it takes 9 keystrokes it is not really a time-saving abbreviation.

Summary: As is often the case when German uses such cryptic abbreviations, English has no abbreviation and it is best not to try to make one up. Don't even bother with the Latin form, even if you're working in an academic text, unless you are sure that the style guide of whatever discipline you are working in allows for them -- they are rarely used at best.