Get a belly band and put a sanitary napkin in it (it has to be a femanine pad, tampons don't work
).
I personally don't like the bands from pet stores, the material is too rough and the elastic can pinch. I'm sure there is someone on here, close to you, that makes some good quiality soft ones.
I've used this on a few boys I've trained, it's not a pleasant experience for them and they do learn quickly.
Alana