Jeannine, I have two perennial bunching onions that I get seed from each year - one of which is Hardy Evergreen. They make wide scallions, but for me, they don't multiply much, unless you allow them to self-seed. I was much happier with the quality of scallions the first year from seed, so while some plants survive the winter, I really don't consider them to be usable as a perennial.
The other bunching onion is either "Franz" or "Stevenson", obtained from SSE when I did a 9-variety bunching onion trial some years back. I don't know which one it is... but it stubbornly refused to die when I turned it under (twice!), so I moved it to a permanent location and kept it. The two varieties are nearly identical; large scallions about the same size as Catawissa (about 1/2" across), exceptionally hardy, and they divide rapidly into large clumps.
Whichever one it is, it blooms later than Evergreen, so I am able to save seed from both... if you would like to try it, I will have seed available later in the summer. I heartily recommend it for its winter hardiness, medium-large size, and rapid multiplication. I noticed in my trial that while some bunching onions have much larger stems (almost like small leeks), those onions had poor winter hardiness, and tended to divide slowly if at all.
I have other multipliers, some which form clusters of small bulbs, and some which form topsets; but I don't know if I would be able to send them to Canada. The bulb-forming onions (one yellow, one pinkish brown) are both exceptionally winter hardy in my climate.
Yellow (from Hmong gardeners)
Pink (sport, possible Catawissa seedling)
For topsetting onions, I too have McCullar's, as well as Catawissa. At one point, I had 3 other heirloom topsetting onions... but they were lost when my rural garden flooded several years ago.
SSE has a HUGE collection of perennial alliums, which they began releasing for the first time this year (my encouragement for them to do so may have contributed to that). They sent live plants, in quite generous quantities. I have planted 10 varieties, so if they do well, I will have many more onions to trade next year.