Try Herbicida-fenoxi 2,4 D . Danilo, Totem 72 SL. Comes in 1 liter yellow plastic bottle from SISAGRO.
This is what we use in fincas in the country side.
You may find it in Montellano. Comming from Sosua just after the shell gas station turn on left. Drive just 100 meters before the end of the road. on the right side facing the mill there is a store specializing on weed killer.