I agree with the others - a Knot is a classic. If I have a dressy occasion, I carry one of my Knots. I'll sometimes pair one with jeans too.
The newer Knot clutches by outgoing CD Matthieu Blazy are roomier, and a redesign of the original. Those will fit a phone easily.
Most us of us responding know and love the Tomas Maier Knots. I have four of the regular size, and one Stretch Knot from his tenure. The Stretch Knots will fit a phone, but the standard sizes are questionable. I can squeeze my phone in my standard Knots if I remove the case, but it does not clasp easily with my phone.
I think both versions are gorgeous, but I have a preference for all the gorgeous Tomas Maier designs I find on the secondary market. If it's an occasion piece for you, and you prefer not to pay full price, I recommend looking at preloved.