Source is very small

I am asked not to enlarge the photos and now they are too small

That's because a source image that is too small to begin with won't make for a good cutout at all.

When you enlarge an image, you don't increase the  picture quality - there are only so many pixels in the original image, and those pixels just get stretched, making an enlarged image either very blurry or very pixellated, which also won't make for a good cutout.

Instead, you need to look for high-quality source images that are large enough to create a cutout - the face needs to be at least 180 pixels tall for this.

tbf, while it's far from an ideal source, it's probably just about worth cutting, since you won't need to upscale the face area too much to reach 180x180, once you crop it.

For example, I reckon you could get passable (if, again, not ideal) cuts from this one and this one (although BramNUFC's newer one is much better), but this one is far too small to bother with, on the other hand.

@NATHAN94 needs to start finding a better quality of images to request, as too much of his requests are unsuitable. Since he's on his fifth or sixth account, one would have thought he'd learnt by now what kind of images we're looking for, but it doesn't seem to have clicked just yet. I understand images for obscure players might not be easily found, but that doesn't mean inferior images should be uploaded instead, or that you shouldn't have a proper search for better alternatives.