I would just go to Kitty's craft room 20 feet away and get a sheet of Hobby Lobby white foam and make them. While you caint do that, you can go to Hobby Lobby.
while i fully advocate for this arts & crafts approach, last time i touched the "special scissors" i was in dutch for a week.
also, broken dot line 20lb paper in matte with a japanese finish not to be used for gasket making. even if you hatch a plan for a clandestine operation to snake a few sheets under the darkness of night. the war department will find out and come down upon you with the fury of 10,000 suns.