Spigot rings for TD2 S2

Hi, I have just bought myself a second hand set of 19" alloys with 255 55 tyres to replace my standard 16" alloys and presume I will need spigot rings as One wheel has a ring fitted. Measuring with a rule and not a gauge I am coming up with a size of OD 73mm and ID 70mm on the spigot ring that I have removed. Can anyone offer any advise of how I should proceed to order the correct sizes, will the VIN number give any clues to the correct size required and any suggestion of where I should buy them. Many thanks, Len