This seems to be the most popular breastfeeding group on Facebook in the Philippines:
https://www.facebook.com/BreastfeedingPhilippines/
Though, I don't know if they focus exclusively on extended feeding. I know that L.A.T.C.H. has a big community here! They're a a non-profit that would more than likely have information that you're looking for.
Check them out here:
https://www.facebook.com/theperfectLATCH/
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Yes Breastfeeding Pinay is the most active breastfeeding group. They tackle everything even extended breastfeeding. They have the most numbers of followers or members too.