As a former banker, having dealt with issues on both sides of the border, if you are a US customer, probably the worst way of paying ETI is to send them a US personal check which they clear through their Canadian bank. You almost have no idea of what value Canadian you are getting for your US. It is a much time consuming from an operational point of view and therefore expensive process of clearing a US$ personal check through the Canadian clearing process. Escape's bank will charge them a fee, which will reduce the amount of Canadian you will be credited with against the value of your trailer. It should be noted that Escape asks for 60 days for personal checks.
The best way is to go to your own bank and ask them for a Canadian $ denominated bank draft. They charge you the exchange rate at the time, and there's probably a fairly small fee for the service, almost certainly less that what Escape will charge you as noted above. If you are a good customer, you may even get no fee as the bank will make some money on the buy-sell rate noted in previous posts. But you will know exactly how many Canadian $ you have paid and Escape gets Canadian $ as well as a bank draft which they will not require 60 days to clear. There may be other banks who could get you a better FX rate than maybe your bank can, but that may cost you extra fees, but still much better to pay Escape in C$ with a bank draft.
There is also the wire transfer route as several have noted above, but again do the transfers in C$ rather than US$. Then Escape's bank will get the right currency and there will be no fees. Obviously there will be some small fees and for those that are happy to negotiate that process that's great. But not everyone will want to go that way. For those that don't, best to use the C$ bank draft route.
Yes I am a Canadian and have a Canadian bank but when we pick up our new trailer next week, I will still take them a C$ bank draft (purchased the same or the previous day) for the balance and will be able to leave without having to give them a check 60 days in advance.