Most likely this is a cut & sewn cover from China or Mexico, so its sold only as shown without a nail trim option. Keep looking and you should be able to find a manufacturer with a similar sofa with nail trim or at least as an option.

Applying nails is a very skilled operation, not for amateurs, you take a high risk permanently damaging the leather.

search google images: leather sofa nail trim

Actually we don't want leather - we just want upholstery. Our cats would make short work of a leather sofa! We're having a hard time finding the sweet spot of the right loveseat dimensions that have all the features we're looking for, so I figure if we just add the nail head trim ourselves, that's one less thing to eliminate for,