I have been in touch with Ken (hardridden on ebay) and he said he would be looking at having the '75' part cut from chrome vinyl and then overlaying this on the printed background before laminating it into the plates.
But this all depends on quantity. So I thought I would also post here to see what response I would get, and hopefully be able to get these made.
Don't know on prices at the moment as it's all just for numbers so Ken can do the calculations.