The font is so small the exact font is not important. You can use a word processor. Pick a font that looks close and type 5416 in the smallest size it allows. Then reverse the colors so the background is black and numbers white. You can print it on paper and then glue it on the back of clear plastic or print it on projector transparency.
Another way to do is take a picture of the cab number. I use a PC freeware application called Irfanview. It will allow you to print that image to the exact size that will fit in your headlight.
Pete