A more expensive but less error prone and a better looking solution would be extending the link between this split keyboard http://www.amazon.com/Kinesis-Freestyle-Solo-Ergonomic-Keybo...
I am frustrated with mine that I can't place the halves wider and was considering something similar.
The Matias Ergo Pro uses a standard TRRS connector between its two halves. You can buy essentially any length on <insert your favorite commodity cable dealer here>.