It is beautiful.
I understand your not wanting to introduce another color but you do what you gotta do. You have several tones to choose from.
My eye picked up the deep navy blue. Do you have some deep blues you could lay the quilt on to take a photo of what they would look like as the border color?
I think it would be stunning if you had enough of your white/cream fabric for the border.
What does your backing look like? Is there a chance it would blend with the front well enough to roll your backing over quilt front and seam it as the binding?
I will look forward to seeing what your resolution is.