This article is from the RSC/UKSC Cricket FAQ, by Ganesh with numerous contributions by others.
Matthew van de Werken:
Probably the most common place for the moisture to seep
in is through the toe. A popular remedy for this is to
cover the toe with "Shoo-Goo", which is a silicon-like
substance that dries hard (like a tennis-shoe sole).
It's designed for replacing holes in soles of shoes,
hence the name, but it works really well on the toe of
a bat. The only caveat I have for its use is that it
makes the toe of the bat a bit grippy, so you can be
running, sliding the bat, and it grips and stops,
which is not desirable!