Some of the old traps work well. Heavy box with a bit of string tied to the
back of it and a pencil tied to the other end of the string. The length of
the string should be just long enough to get to the other side of the box.
Put a lump of toffee round the middle of the string and place the box where
you know the mice goes. Prop the box up with the pencil so that it is just
on the verge of letting the box drop. Mouse comes along, smells toffee, goes
under upturned box, leans on string and tugs at toffee, pencil moves and
down comes box on top of him.
In the morning slide a piece of hardboard under box and off you go.
Box has to be heavy enough and not made of anything daft like cardboard
which he would just chew through.