The Robinsons Mall handyman sells the dielectric grease in a small sachet 29 Php it is in the locked cabinet in the automotive section at the bottom of the cabinet.

 

From experience in buying replacement parts here, I doubt you will find just the connector. They will try to sell you an entire cable. But you will find good quality electrical parts at Polaris. A crimp on connector made off copper alloy. then use a electrical contact grease to coat the positive post and connector. If you take the cable there they might even crimp it on for you.