There are a few lockers available for the 14bsf axle:
ARB Part # RD40
Detroit Locker Part # 225C-135A
Power Trax Lockrite part # 1950
Power Trax No Spin part # 92-07953305
Detroit's are easily the most reliable locker out there but the Power Trax lockers are very simple to install, cheaper and meet the needs of most wheelers. ARB's are the most flexible (fully selectable) locker out there and work extremely well but they are the most expensive and they require regular maintenance (checking for air leaks, checking compressor, etc.) ARB's are available for the 14bsf and the D44.
If I had unlimited funds, I would get the ARB in front and in back.