It looks like the French Microsoft Store has outed some new Mozo covers for the Lumia 550. So far, only two covers are listed. One is a smooth, rubber coated Cyan colored cover that replaces the stock battery cover, while the other is smooth black flip cover with a flap that closes magnetically and sports slots for credit and debit cards.
Though Mozo was touted as an official partner for Lumia 950 and 950 XL covers, it wasn't clear if any Lumia 550 covers would be released as well. Unfortunately, neither of these new cases is actually in stock on the French Microsoft Store just yet, but take this as an indication that they are indeed coming at some point. If you'd like to check them out, however, be sure to hit up the links below.
Update: And here are the Microsoft Ireland listings!