"If you do not meet those minimums, we charge a monthly activity fee. Generally we waive this fee for any month in which:
You have more than 100,000 USD in equity or
You generate more than 10 USD in commissions and fees."
Either:
(1) trade on margin: buy the usd bond directly with your hkd as collateral. That may cost you some interest charge but you can buy more than what you deposit. (Of coz, it is subject to margin call)
(2) do a fx trade to buy usd first and then buy the bond u want. This way will not give your leverage but do not involve interest charge and no margin call for sure.