Depending on the shirt and material you can go to a store which makes the jerseys for youth teams and semi pro teams and have them make a patch. They can iron vinyl lettering to a piece of light fabric then just sew it over Keanes name and number. I am sure their is a sports shop in Liverpool that makes team kits.
Its honestly not too much money and they do it all the time. I did it for a real nice Hockey Jersey I had. It was an official NY Rangers NHL League jersey and I turned it into a Messier jersey. Cost me $25 and they sewed it all on for me and made the name plate.