Do you mean the nameplates that are attached to API 650 tanks (Petroleum and related products welded storage tanks at atmospheric pressure)? According to the standard, it's the tank manufacturer obbligation to provide a nameplate containing, as a minimum, the information listed on the standard.
If you're the tank purchaser, demand the fabricator to furnish the nameplate. If you're the fabricator, then you'll have to make the nameplate. I doubt that you can buy it ready, because you may want to include some extra information that the standard doesn't require.
It doesn't need to be an artist's masterpiece; just a rectangular piece of stainless steel 1/16 of an inch thick with the tank data written on it.
Here in Brazil there are artisans who make those nameplates, ranging from identification of men and women's toilets to plaques in cemeteries. I'm sure in the USA you'll be able to find such an artisan. Look in the yellow pages.
Good luck
Giovanni S. Crisi
Sao Paulo - Brazil