Irish Black, White pudding
Black pudding should be fairly easy, but white is much harder to find. I get mine driven over the US border or flown in, but there are some possibilities here.
For black pudding, haggis, and possibly white pudding try Allen's Scottish Butchers on Weston Road in Weston and Meat on the Beach on Queen Street in the Beaches. Do call first. I've also heard that there's a Scottish butcher called But & Ben Scottish Butchers & Bakery at 1601 Ellesmere at McCowan in Scarborough. There's also crawfords in Niagara Falls.
I've not seen an Irish butcher in the GTA.
I've been to the Mrs. Bridges location at Eglinton Square so can vouch for the general quality. I haven't had the pudding, though. When I'm that neighbouhood, I always go to the Tara Inn on Eglinton for 100% authentic Irish fare.
Here's (I have to say it) the link of the Irish: