Looking at the parts list, you are missing a spring washer, the lever and the screw. The only way you are going to get those parts is to either find another one and scrounge the parts or find someone who has one. I have a couple off of old Voits levers but I doubt they will fit..and I don't have a DR-2 to test with. There are 2 other options, just use it without one or plug the hole. As long as you don't intend to use the J valve you really don't have to have the lever, just set it to reserve and go. The other possible option, and I would have to see it to determine if it would work, is to just plug the port. All of the old Voits and the Dacor 400/800s came in 2 models one with a J valve and the other without, the only difference was a plug was placed in the port instead of the valve assembly. Also, those regs had an optional plug that could be installed in the J valve hole that was tapped for a SPG, that is another option if a plug will work. I have made a bunch of those for the Voits, don't see any reason I could not make one for the Dacor.
My first shot at getting the parts would be to ask on VDH, I know at least one of the guys there was a Dacor dealer in the past and has some old parts or one of them may well have an old DR-2 for a good price. If all else fails, shoot me a PM and we can discuss making a plug.