I now have 12" (330mm) conical busks in stock at www.sewcurvy.com.
They are sturdy yet flexible, made from stainless steel in Germany. They have a bit more spring than the thicker stainless steel straight busks.
I am offering them at the special introductory price of £10.00 for this week only, then they will go up to the regular price of £12.00
Edit: My online shop is priced in GBP sterling and the payment gateway is Paypal who have their own exchange rate which changes daily. If you are paying in Euro's then the price is about €11-13, and if in USD then the price is around $16-20. Those are my best estimates today.