What's best way for me to lock in today's exchange rate to hedge FX risk on a trade?

I’ve put on a trade involving securities denominated in both Canadian and U.S. dollars. In addition to the risk profiles of the underlying securities, the trade is also susceptible to exchange rate fluctuations: in this case, even if the underlyings move in my favor, any trading profits would disappear if the USD:CAD exchange rate dropped from today’s ~76% to ~74%.

Now I’d reap similar BENEFITS on my trade if the rate went UP (to 78% for example), and [U]my original plan had simply been to ignore the currency risk altogether[/U], reasoning that no one can reliably predict the direction of FX movement, so as long as the benefits I’d reap if the rate moved in 1 direction are equal to the losses I’d sustain if it moved against me (they are), then I’ll just roll the dice. IOW, if it’s a +EV trade, then as long as I’m willing to bear the FX risk, I should be willing to put it on.

HOWEVER, [B]I’d now like to understand just what it would cost to hedge / insure against the FX rate moving against me[/B]. But I’m not sure what instrument would best serve that purpose. What’s the cheapest and most flexible FX instrument I can buy to protect my securities investment against a downward move in the CAD?

Bump, any help?