Random champion shard for IP in store yet? And getting mastery 7 tokens before mastery 6?

Hi,

I can't seem to find the ability to unlock a random champion shard for IP in the store. I have been lucky enough to get almost exclusively skin shards in my chests, so I don't have enough champion essence to unlock mastery level 6. I already have two mastery level 6 tokens for a champion. If I keep playing that champion, can I get mastery 7 tokens with them, or do they need to get upgraded to mastery 6 first?

When will the ability to buy champion shards come out, so I can get mastery level 6?

Thanks!