The issue is you need something that is high resolution. If you start printing off the internet your printer is “guessing” the color of three out of four pixels. That is why they are fuzzy.
Do a search for high resolution maps, or “vector” images that are line drawings that will extrapolate to larger sizes.
I doubt you will find any for free.
It’s not really the “fuzziness” that’s a problem, it’s the propensity to show local roads as white on a beige (etc.) background. But, your point IS well taken! Stamen, who I mentioned, isn’t too bad in some versions, about how the image prints, but, their maps are more limited in other ways.