Measure the height of the numbers, find a local stamp making shop and get one made. By the time you pay for shipping twice, those fees would have probably equaled or exceeded the cost of a stamp. Remember, printers measure in 72nds of an inch. If you provided them with an exact decimal or fractional measurement, the shop would convert it to 72nds. As to the font, a picture would be the best bet. I tried the ones displayed for forum messages and the "2" is the problem.
Jim