Hi Marty,
The blank Williams coin entry plates are available at Pinball Resource (I said Marcos before but that was wrong). See here:
http://www.pbresource.com/CoinDoor.htmlIf you get some I can email you the print sheet for the decals and you can print them out using a laser printer onto waterslide decal paper and apply them yourself.
PBR has the "Dollars" one for sale so you only need to make the "20c" one.