After opening the eShop, switch to the "NintendoswitchOnline" section on the right, scroll down, and you should be able to see it. It should be noted that since the "Loss Voucher" in the Hong Kong server can only be purchased directly on the eShop, only Visa/MasterCard credit cards or balance payments can be used. If you need to use UnionPay or Alipay, you can consider purchasing a prepaid card for recharge at the Hong Kong Nintendo Store, and then use the remaining balance to purchase coupons.