healthwick.ca is my go to - prices are reasonable and shipping isn't ridiculous
agecomfort.com - be advised they apparently send catalogs and stuff, also their return label on the box says age comfort on it
daynitecare.ca - if you're out east this might be a reasonable source, however if you are out west be advised they will tack on extra shipping costs after the fact
Rearz is in Canada - you can usually find better prices than buying direct if you shop around unless they're having a sale
ABU has a warehouse in Calgary that you can pick up from - not a physical store though
Trinity Home Medical in Edmonton has a physical store
Universal Diapers in Toronto has a physical store with lots of stock