I've not seen a 'splitter' for Loconet as such anywhere on the market, but if you use Digitrax's UP5 panel you can utilise the extra socket on the side as well as the 2 main ports on the rear to provide 3 RJ12 ports. hence feed into one of the 3 ports and out of the other 2.
One word of caution - do not complete the loop! In other words do not join the clockwise and anti-clockwise sections at the other end. This would cause all sorts of problems