Hi
I don't have any experience of SRXs but used a company called Venhill to make up longer cables for me. You will find them if you google the name. All they needed was a standard pattern, so an old cable of the standard length, and a measurement of how much you want added in. I seem to remember they were reasonably priced and the cables were well made. I also seem to think they do brake lines as well, but I could be wrong about that.
Spartacus