Exchange US dollars

I work at the border. You can bring whatever amount of money into Canada as you want but if it over 10,000cdn or equivalent in foreign funds you must declare and do a FINTRAC form. Super easy... in fact we fill it out, you just sign.

DO NOT structure your money. ie: I have a friend hold some. It's just a form of smuggling and it'll be seized as proceeds of crime.

The seller only wants cash, so I'd do what you did, go to Canadian bank and pay the conversion fee. It's crappy but to buy that car you just have to do it. Unless he'll take a bank draft....

Good luck on your car purchase.

Riddler