Delrin as far as I remember is just a trade name for "acetal" which is available from a number of manufacturers.
Another good material for cones is PTFE if you can get hold of any offcut or samples. Failing that, both polypropylene and nylon work well also.
As an aside, I have loads of white 3mm thick polyprop sheet, no good for cones but if anyone wants some bits, pm me as I can take with me to York next month.