Hey I'm looking for the same thing and the only one I came across was the LG 27uk850. While it's not 5K like the iMac, it does look pretty sleek, provides 4K quality in an IPS panel and it's simply the most affordable 4K usb-c monitor I could find coming in around 500 dollars.
Now you could also wait for the upcoming Apple Pro display which is rumoured to be a 6K display in a sleek form factor. I do, however, expect this display to be quite pricey and well above the thousand dollar mark. Also, it's unknown whether or not your MacBook Pro will actually be able to handle a 6K display because it lacks a dedicated graphics card.