Apparently, they can be.
I doubt cleaning them will make them any quieter but that's where I would start anyways.
If you are set on buying new ones, Rockauto has the 21 lb "pink" injectors but they aren't cheap.
I've used Seafoam with some good results. There is another product called Star Tron Enzyme Fuel Treatment ($8.99/bottle) that even got my old hasn't been used in years gas powered edger running like it was new.
I'd definitely try this stuff before changing injectors.