O-gauge Traffic Cones

Beg, steal, buy or make one the size you want ( cones vary a lot) Make five or 10 plaster of paris moulds of it, spray the inside with the cheapest spray polish you can get. Leave to dry, then cast using low modulus white acetoxy - cheap white builders silicone filler, leave to dry and paint the red bits as required.

In message , Mac writes

ModelScene (available through Peco) do them in OO. I suppose if the worst came to the worst and you weren't able to get any in O you could use OO ones and imagine they were the right size.

Sounds like a repeat casting job to me. If you'd like me to have a go at it for you contact me off list.