I think I may have found a solution:
an item with a unique passive: 1 second reduction on all cooldown whenever you kill a minion.
Because dominion has a much lower minion count per game than normals in SR, this wouldn't be too OP would it?
Of course it would still have to be a pretty costly item, not something that can be bought very early in the game.
Something like Fiendish Codex (1245) + Kindlegem (850) + 605 gold = 2700 total gold
250 Health, 40 AP, 10 mp5, unique 20% CDR, unique passive of on minion kill to reduce cooldowns.