Not meaning to be rude here, but your kid is 4. Kids at that age should have a full time job of having fun - and attending two schools a day, every day, is not fun. Considering how much homework (yes!) that local kindies make their students do, and how much pressure these kindies put on the little kids, I honestly do not think this is the best or fairest thing that you can do to your kid.
If you want to "supplement her learning" (again, for buddha's sake, she's 4!), take her to the countryside/pools/sports grounds in your free time. Read books together. Even a trip to the local supermarket can be turned into a "learning opportunity" - but one that is fun and good for bonding.
However if you insist on putting your kid in two schools, there is loads of info on the Geobaby and GeoSchools sites. A quick google search for Montessori would also bring up some names.