Which are the best drool pads for my baby carrier?

I think cotton with inner cotton fleece is good and absorbent. You can join the Facebook Babywearing Singapore group https://www.facebook.com/groups/245166299015337/ and find out what babywearing accessory makers there are in Singapore. They cost between $15 - $30 depending on type, material and fabric choice. Alot of them are WAHMs so good to support local talent!