Black Pudding in Denver area
Conor O'Neills in Boulder has an Irish breakfast that includes two eggs, toast, grilled tomatoes, roasted red potatoes, Irish bacon, Irish sausage, and both black & white puddings. It's the hangover cure to beat all others (and available as a half-order, when you're not THAT hungover). I like the puddings quite a bit, though not having had them in the mother country I don't know if they're traditional.
Euclid Hall's blood sausage is great.
While I haven't eaten it yet, the Continental Sausage Company appears to have a Blood-and-tougue sausage and the other Continental sausages I've eaten have been outstanding. They've got a location in Cherry Creek (which is a small grocery store combined with a small deli) as well as a location in Arvada which is apparently more of a sit-down place. I didn't see the blood/tongue sausage on the menu but perhaps you can ask for it and they'd serve it to you? Otherwise, I'm sure you could get some to take home.
Also looked around and saw that Jordan's Bistro & Pub (S. Univeristy & Evans) has an Irish Breakfast on their menu with black pudding, et al. Not sure if it's any good and now I've got a new place to add to the food list.