What is a rare suit? We don’t exactly have drop chances in this game. 
There might be suits only available from carryover that are impossible to get. Especially if they are suits that required a certain H2016 progress. The most unlikely one to have is the Black Winter Suit which requires to have killed an Elusive Target in H2016, link the IO account to H2 and then transfer progress from H2 to H3.
The other suits not currently unlockable without fitting carryover is the Santa Suit, the Wetsuit and the Snow Festival Suit. Though these likely come back at some point.
Also check out this great list of all unlocks, sorted by how to get them: