I've kept bowfins but they were wild-caught by me. I think the last time I saw them for sale was at Big Al's in Yorkdale Mall, Toronto...back around 1985...and they were listed as "Chinese Bowfin", likely to get around some legislation that might have impacted their sale.
There was also a small LFS in Pickering, Ontario (just outside Toronto) that sold "Chinese Bowfin", "Asian Grass Pickerel", "African Crappie" and other fancifully-renamed locally-collected species.
I will mention that I have contacted Jonah's Fish and inquired if they would ship to Canada...and they didn't even bother replying. I have no other suggestions.