Once you have the multicurrency feature turned on, QuickBooks Online enables you to choose among a myriad of currencies when setting up customers and suppliers. I'll be happy to show you how.
To add a supplier with their foreign currency is a pretty straightforward process.
You're now ready to record transactions in the currency you pay your supplier with. For more on how to set up suppliers with a foreign currency in the system, check out this article: Add a supplier with a foreign currency in QuickBooks Online
I hope this helps! Feel free to stop by if you need anything else.
As another option, you may utilize one of these services to pay your bills. You may keep pay it in CAD and your vendor will receive the payment in USD.