where can I get a carb repair kit for a landscape Sgt 34x grass trimmer ?

Not sure of this brand but check for any manufacturers marks on carb Eg Walbro, Tilotson etc along with model numbers. There are places that will sell a reair kit for the carb make/model rather than the machine manufacturer. I have udsed Central Spares in Wimborne Dorset. They have a good selection and a good web site. Diapragms are not usually to hard to fit just make a note when removing old ones for things like which side of the diaphragm the gasket is as this will affect diaphragm travel/operation.
Hope this helps

Robin
October 2014