Buying TST 507 TPMS in Canada - Where is good?

I know, it's a pain.

Bought mine from the manufacturer while I was down in Florida.
Free shipping to the campground.
But we still had to suck up the exchange rate.

You might check with TST to see if they'll ship to Canada via USPS (Postal Service) which is usually way cheaper than the couriers when crossing the border. There may be others who will.

Good luck.