The bear range trailing stop indicator, as discussed in "Profit Locking And The Relative Price Channel" by Leon Wilson, is available for download here.
Once downloaded, from within the NinjaTrader Control Center window, select the menu File > Utilities > Import NinjaScript and select the downloaded file. This indicator is for NinjaTrader Version 6.5 or greater.
You can review the indicator's source code by selecting the menu Tools > Edit NinjaScript > Indicator from within the NinjaTrader Control Center window and selecting WilsonBearRangeTrailingStop.