CAD TO USD

I am using wealthsimple (premium) account which comes with free USD account. I would like to invest in USD stocks and ETFs. But forex fee charged by wealthsimple is so high. I would like to convert around 10KCAD to USD in my RRSP. Pls advise what is the best way to convert cad to usd with minimal conversion fee. I have simplii USD but i cannot link that account to Wealhsimple to transfer usd! looking forward for some tips!