"suitably dressed" is correct and usable in written English.
It means someone is dressed appropriately for a certain occasion or activity. Example: The guests at the wedding were all suitably dressed in elegant dresses and suits.
Doctors warn, however, that sleeping in the cold may not be suitable for everyone, and that babies should be suitably dressed for cold weather.
Get over here, Miss Suitably Dressed, and start selling!
They were to be unmarried, pious, non-political and suitably dressed, preferably in a clerical collar.
It might often be studiedly casual and suitably dressed down, but it's a uniform just the same.
Suitably dressed, I was able to march out alongside the man charged with getting every backstage detail of the 1987 FA Cup final correct.
We were then greeted on stage by Dennis the Menace diarist and author Stephen Butler, who was suitably dressed up as a magnificent ringmaster.
The next week, on the Friday, there was a knock at the door when I was hoovering the staircase, and I realised quickly I wasn't dressed suitably for company; I simply never had company.
In fighting trim, Mr. Clooney looks suitably sleek, even when dressed in the generic business clothes he's soon packing into a suitcase, a task that's captured in a series of precisely framed, rapid shots.
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The ever-exuberant rapper took to the stage tonight to perform a much-anticipated duet with Florence Welch, dressed in a suitably spangly silver mini dress.
She's dressed in a suitably futuristic silver robe – a 72-year-old, playing an instrument that's 50 years old, making music that retains a utopian and optimistic vision of the future.
