There IS some magic available. At least magic in the same sense as some isolated tribes could see the western technology when they met first time.
The magic I'm talking is image enlargener. I have used it uncounted times when one has had a screen resolution image and wanted it to be printed at the same or bigger size in centimeters as he watched it onscreen. Every time it had been the last resort, when there were no possiblities to get the real hires image soon enough. Every time the explanation was the same: "I was sure (or I have been told) that these images are good because they look out perfect onscreen"
If this is also your case, try the same magic. Image enlargeners can make a screen resolution image to same centimeter size or even larger image with print resolution. That happens without adding jaggines or making the images fuzzy.
Image enlargeners guess where there should be a sharp edge or a thin line and keep it narrow. Larger forms are made bigger by interpolating the missing intermediate pixels For example In good enlargener cat's whiskers do not get thicker altough you increase the pixel dimensions to 400%.
NOTE that the information is not increased. No program can guess a detail which were lost due too low resolution. A small dot which would have been visible, if the original photo was 2000 pixels wide, do not appear if you enlarge a 500 pixels wide photo to 2000 pixels.
The best enlargener I have met is ON1 Resize, ON1's product is old. It has been sold as "Genuine Fractals" and "Perfect Resize". ON1's product just was the one that didn't make cats whiskers thicker.
On1's software has premium prices. But there's also freeware. Smilla enlarger is well worth of checking.