Amidst all of the cost rebalancing for Champion-level rewards in the Argent Tournament, the CMs have indicated that there would soon be new ways to obtain Champion's Seals. With the advent of patch 3.1.2, it seems Blizzard has started to follow through on that!
We received a bunch of tips in the mail over the past day or so, all letting us know that their Champion's Purses -- one of the reward choices for Champion dailies -- could randomly contain a whole 'nother Champion's Seal. This is a pretty big deal, especially since you have multiple chances per day. Players are reporting the percentage to be somewhere between 25% to 50% per Purse.
Not too shabby! This also means that those mounts you want -- including the recently-reduced Argent Hippogyph -- might be a little more within your reach, and faster at that.
We'll keep you informed of changes sure to be forthcoming, given that the CMs also mentioned that the Hippogryph cost reduction was (in part) due to their desire to add even more rewards in future patches.