Mortise lock. Help please

Hello,
My sliding glass door lock broke.  I have bought 3 different types from home depo and they dont fit the face plate. My house is only 4years old and I cant imagine this is something special custom thing. When I look up this company seems to match the look. Can you help me? Is this one of your parts? When I measure the inside plate instead of standard 3 3/16" or 8.1cm, I measured 7.8cm .. which is a odd measurement. 
Thank you for the help,
Kim