If M a monoid and $Set^M$ a topos associate to M, I found $Set^M$ have (epi, strong,mono) factorization system(http://math.stackexchange.com/questions/541300/epi-mono-factorization-in-presentable-categories), I think $Set^M$ has (epi,mono source) factorization [http://katmat.math.uni-bremen.de/acc/acc.pdf, pag. 257] but I can not found the proof of that, I would like see some reference of the proof such that don't use the fact $Set^M$ is a locally presentable category or If I suppose it's wrong a liked see the counterexample.