You can use Norbet's Gambit to convert between USD and CAD either direction. I have never personally done this, but I am planning to convert some CAD to USD soon, so I can invest in USD index funds without paying the typical 2% conversion fee.
You must be okay with waiting a few days for the trades to settle, and okay with the fact that the exchange rate will almost certainly change before you sell the shares in the opposite currency.
The spread on DLR.TO is about 0.01% - 0.02%, and you also have brokerage commissions and fees. If you use a discount broker the commissions and fees can be quite low. EG. To transfer $5000 USD to CAD using Questrade, you would deposit the USD into a Questrade account and then purchase ~500 units of DLR.U.TO , since it is an ETF there is no commission on the purchase. Then you request that they journal the shares over to DLR.TO and you sell them in CAD (will have about a $5 fee in CAD, and lose about $1 on the spread) and withdraw. The whole thing will have cost you $6 CAD, in lieu of ~$100 you would pay if you did a straightforward conversion with a 2% exchange fee. The difference in fees scales up as the amount you transfer increases.
Someone has posted the chat log from when they requested their shares be journaled from DLR.TO to DLR.U.TO here. It looks like it was quite straightforward.
Of course there is a time-cost, and the nuisance of signing up for an maintaining an account with a broker if you don't have one already. You can do it on non discount-brokers, but it will only be worth it to do it with a larger amount of money, since the commissions are larger.
Note: If you have enough room to hold the CAD amount in your TFSA and will still have that much room at the end of the calendar year, I recommend doing the exchange in a TFSA account. The taxes are minimal unless the exchange rate changes drastically while your trades are settling (from capital gains or losses while waiting a few days for the trades to settle), but they are annoying to calculate, if you do it often. Warning if you do it in a TFSA be sure not to over contribute. Every time you deposit counts as a contribution and your withdrawals don't count against the limit until the next calendar year.