Have a word with Joe at David's Tyre Shop on the left hand side as you leave Sosua towards Cabarete... he is most helpful and knows lots of people so may be able to help.
If don't get it in POP go to REPUESTOS DANILO HIDALGO, this is located on Autopista Duarte 8 Kms. before you get to Santiago next to Dicoteca Champion Palace.