What is it for and do you it need to heat treat it. If you don't live to far from (Nottinghamshire) me I have some 1/16 by 2" wide gauge plate which is the equivalent spec to silver steel and what length do you need. Send me a message if any good.
Thanks for all the replies. It looks like I!'s probably not available. At least not in the very small quantity I need at a sensible price. I need it for a maintaining spring in a clock barrel. What matters is stiffness after hardening. Doing some sums just now it looks as though a round section would need to be about 20% greater in diameter than the side dimension of a square bar for the same stiffness. So substituting a round bar for the 1/16 square bar would means I would need a round bar 0.075 diameter. This is pretty close to 2mm, which is readily available size. So I'll go with that.