Short of buying a case of regular retail packages, there are no bulk packages of 45-70.
If you're looking for toasty factory loads there aren't many options available in Canada. HSM produces some hotter loads with hard cast bullets that would be suitable for dangerous game that I've seen on the Cabela's site and they're $50-60 for a box of 20. Search Cabela's for "HSM" and the first result is the "Bear Load" in 45-70.
There is also Buffalo Bore being offered some places now but that'll be closer to $80-100 per box of 20.
Unlikely to get more than 5-10% savings if you buy by the case (and you likely can't because the stuff is so rare).
Hornady Leverevolution loads are a little warmer than some other factory loads but aren't elephant killers or anything. They are also a tipped expanding bullet so I don't know how effective they'd be against bigger bears like grizzles.
The .45-70 is a perfect candidate for reloading since it can use such a wide range of powders. Get some level 2 load data (level 1 replicate black powder loads, level 2 are for modern levers, level 3 are for dropping block singles like a Ruger No.1), a pound of a suitable powder (there are many that will work in a .45-70), some large rifle primers, order some hard cast bullets from the Bullet Barn or elsewhere (these don't expand much at all even going through heavy bones), pickup a $30-40 Lee Loader kit, get a rubber/plastic mallet from your tool box, and you can (literally) hammer out some handloads of the desired power level for $1.50/round. The Lee Loader will pay for itself after 10 rounds.
The Lee Loader is so simple you can do it on a tree stump in your backyard:
