Booking Travel outside of Asia

I am new to Hong Kong and am curious about the best way to book travel (internationally not domestically). Of course, I have searched online for the lowest prices and found many suitable flights on various sites. The problem I am running into is that very few of the sights allow payment via union pay. The bank account I opened locally only provides a union pay ATM/Debit card. I went into the bank today to speak to them about this and they told me the only option for a Visa/ Mastercard is to open a line of credit. I would like to avoid having to do so and use my union pay card as payment if possible.

I am wondering if someone knows a travel website which allows union pay to be selected as a form of payment. If not, maybe there is a good local travel agent on Hong Kong Island that someone can recommend that would accept union pay. Thank you :)