Also be sure that it’s really leaking from the top, and isn’t leaking from the seals between the reservoir and the master cylinder. When those seals die, you get all the drips of a reservoir leak except for on the reservoir itself, and since the reservoir is often dirty and oily it can fool you into thinking the leak is coming from higher up than it is.
If it IS leaking from the reservoir top, then once that’s fixed clean those seals very well because the inner surface of those seals are impervious to brake fluid, but the outer surface often is not, which will allow the fluid to dissolve the seals from the outside in and cause a leak.