The only GPS you can get for the Philippines are the open source ones. These are just as good, if not better than the other country maps for sale as they are usually updated daily as users as new stuff.

Their are 2 available but the best one is FREE OSM-PH Maps for Garmin GPS

The map is only available for Garmin, but you can pick one up fro about £60 on Amazon

If you do use the map, please Donate to them.