Milgard composite slider Missing handle and reciever

I'm not sure what handle you had originally, but if you have a basic 3-15/16" hole center spacing then you have a lot of options. Start with the 82-030, which should be compatible with your old mortise. I would just double check your hole center spacing to be sure they're 3-15/16" and not 4". We unfortunately don't have a handle with a 4" spacing, but 3-15/16" is common.

You don't need two activators for you mortise latch. You only need one to activate the lock. The reason why this mortise has two activator holes is to compensate for thumb levers that may be installed at a different position, depending on the handle design.

Sure that'd be the 82-249 keeper. This is specifically designed to work with mortise locks like the 82-265 or 82-259, which I think is what you have now.