There is no flag on the dress uniform

An Army dress uniform is appropriate for ship's dress night on a cruise ship. However, the person wearing the uniform must be on active or reserve duty.

where do I inquire about getting sized for a set of Marine corp dress blue uniform?

Regular Class A uniform, which I think is now the Dress Blue Uniform.. when I was in, Class A was what is now called the Army Green Uniform. Either one will suffice.

There is no flag on the dress uniform