Why need pcie 3? Pcie 4 ssd can use on pcie 3 system. Unless u try find tlc then that's different requirement.

Many reputable online store. All IT, EIT, Mono digital, brightstar. Shopee Mall or LazMall also have Sandisk official store I think. If in doubt try search in lowyat for review. Just make sure it's the real store, not a fake store using the real store image. For example a random .my name store using EIT store image in their product. Some store also have sus listing, like seagate agent store selling wd drive.