grab bar number plate

[TRX23rider]

i need a number plate but i dont have time to order one. Has anyone made one that looks decent. what should i make it out of and how big?
thanks

[Phills450r]

my first race i didnt have one and i used one of the track owners signs... he let me cut it into the shape of one and it worked good.. it looked like cardboard but wasnt im not sure what it was.. go to the local honda/yamaha dealer they should have them?? well mine do