Canadacan...I just had a friend come into Montego Bay and they did not have Titos vodka...I'm not sure if this is just a temporary/stocking situation or if they've completely stopped selling this item.
Titos is sold in a couple of shops in Negril...crazy expensive the last time I checked in December...approx 6000+Ja.
Again, there's no Costco...but you can pick up your mixers easily at the Mega Mart or other grocery stores in Montego Bay.