Bummer on the replacement mate ... it doesn't sound like you bought a "new good quality one" seeing as it broke a few weeks after you bought it.
Robinsons are more expensive as a local go to, but sell decent quality range from which to choose on a lot of clothing and accessories, and if there's a problem they'll be far more likely to replace/exchange.
If there are any bootery's as Thai's often call them - shoemakers, (don't know CM that well) they might be a go to for repairs and new belts.