Hey guys, we've added the Mastery Flairs to our subreddit, sorry it took me so long to sort it out. How to set yourself up:
http://flairs.championmains.com/profile
Users log in using their Reddit account (uses Reddit's OAuth2 system, so the site only gets public info like your Reddit user name). Then they can add one or more summoners (from any region) and verify them by temporarily renaming a rune page with a generated code. The site sums champion mastery points from the summoners and takes the highest rank and can show that data in subreddit flairs (using /u/ChampionMainsBot).
Merry Christmas everyone, happy holidays! If you need any help setting it up, just comment below and I'll try to help you out!