These guys do clipper repair as well as blade sharpening. I do not know about their expertise with Listers, but it may be worth calling to see. They are local to me, but work by mail as well. I have used them for several years and have always been happy, including sending two clippers for repair. They did a great job fixing one pair. On the other pair, they called me and said they could do x and y for minimal cost to get them running, but that z was going to cost more the clippers were worth and asked how I would like to proceed (which is always a good sign!).