No other "comparable" seller with variety of choices that I've found.
There is a seller of a built 280 AHr battery in northern Alberta, Grande Prairie, on Kijiji that has decent prices, given that he does all the build work, top balancing, capacity testing etc. and his cost also includes fixation AND you won't have to buy extra tools, the expensive to Canada charger / capacity tester or the other components for a DIY build. I almost went that way and still not sure if I should have or not due to the added equipment costs and some stress that I will have building my own battery..
Here is his link.
https://www.kijiji.ca/v-buy-sell-other/grande-prairie/lithium-battery-packs-solar/1581996362 . I had contacted him last year and received a reply but he didn't offer many options then. Now he offers an optional case but still only 1 battery type, 280 AHr. I did not ask him about shipping costs and options. I have no other experience with his builds but the photos look quite good.
My order last week from 18650Batterystore.com for 8 - 304 AHr batteries plus BMS. No Canada Custom Import Duties. Only the usual sales taxes.
There were the normal GST/HST/Provincial taxes, dependent on the declared value / invoice in the paperwork from the seller.
There may / will be Broker fees charged by the courier if you choose the courier to get the shipment through Canada Customs. You can maybe save some money by doing the Canada Customs clearance yourself if you can go pick up the shipment yourself.
18650Batterystore.com was EXTREMELY EASY, efficient and shipment was delivered by UPS in 7 days, to the nearest city for me to pick up in the north. Whereas my 1st order a year ago, from Alicrapa China which was a F-Fest by the seller and took weeks and weeks and full of BS and run around and stress, including a supposed fire to cause delays and shipping cost was MUCH more expensive than UPS from Georgia USA. It also did not have "Import Duties" but only Federal and Provincial Sales Taxes and again the shipping company Broker Fee to get it through Canada Customs.
I only wish that 18650Batterystore.com had even more affordable to Canadian components / accessories and equipment and information, so as to avoid options such as, Amazon and AliExpress and AliCrapa sellers.