Did you try funding an HK account with a credit card? I didn't actually go through with finalizing a transaction, but it charged my card for verification, so it seems like that might work.
PCGameSupply is reliable, but there's an obnoxious buying limit that prevents you from buying a 500 HKD card.
I don't trust myself using CC to fund accounts plus no one in my gorpu has taken the offer of it. Tried PCGS, but like you said it wouldn't let me buy the cards because of the daily spending limit... it was only over the limit by 98 cents.. ugh so hard to get cards