It is tough to find a USB-C to DisplayPort Cable or USB-C to DisplayPort Adapter. I have not found any physical stores in Singapore selling it yet. Instead, you have to get it from online stores like Lazada or Amazon.
For USB-C to DisplayPort cable, I bought mine from Amazon as there are more choices to choose from.
It is retailing for JP¥3,110 (JP¥2,880 before tax), but if you spend more than JP¥5,000, it is tax-free. On top of that, if you pay by VISA credit card, you get an additional 5% discount.