OFA + rewind

I had I thought that most people probably had. Eri's power rewind, has the capability to rewind time for a person. (Simplified) And one for all (OFA) is a culmination of powers of all previous users created to defeat all for one

In the final battle izuku loses OFA and all might has no power left in his body. If we treat One for all as a normal quirk (ignoring the plot and limitations) then eri could theoretically rewind izuku and toshinori to a time in which they both still had one for all, in theory making two copies of OFA.

This is just speculation and theory, they didn't do this in the show or manga because it would make the entire series just not make sense. Eri's quirk has no known limits so theoretically this is possible although there are a lot of problems that could happen and paradoxes that couldn't be fixed.