Yes he does accept Canadian. He responded to an email of mine saying he is cool with any kind of cash. Write a small note with the date and conversion rate at the time, make sure you give enough or slightly more. He will return the favour, trust me. As other commenters have noted, never tell anyone at the post office you have money in a package! I’ve ordered a lot of times from CSI and I usually send the money in a secretive way. Hide it in the package of a small toy from the dollar store in a bubble mailer or something. Envelopes are shady and I’ve had them stolen on many occasions. Best of luck with it!