You are caught between a rock & a hard place simply because of the very limited choices you have in the 235 55 18 size. Having said that, you can get the new Toyo Open Country H/T here in Canada now so you might want to consider ordering a set in your size & have them delivered down to you.
http://www.toyocanada.com/products/OpenCountryHTEN.html (click on the right side that says get data icon to see tire sizes) & contact Toyo Canada directly to find a dealer that will ship them to you or drive up here to have them installed. :whistles: Here is their contact link:
http://www.toyocanada.com/contactus/contact_Gen.html
Or you can try www.toyo.com & ask them when the Open Country H/T will be available.
Other than that, these are your only other choices:
http://www.tirerack.com/tires/Compare1.jsp...at=All&x=4&y=15
Let us know what you have decided, but out of the 3 total choices, I'd personally go with the Toyo myself. B) I hope this helps & Good Luck!